Sexual intercourse

Sexual intercourse (or coitus or copulation) is sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure, reproduction, or both.[1] This is also known as vaginal intercourse or vaginal sex.[2][3] Other forms of penetrative sexual intercourse include anal sex (penetration of the anus by the penis), oral sex (penetration of the mouth by the penis or oral penetration of the female genitalia), fingering (sexual penetration by the fingers), and penetration by use of a dildo (especially a strap-on dildo).[4][5] These activities involve physical intimacy between two or more individuals and are usually used among humans solely for physical or emotional pleasure and can contribute to human bonding.[4][6]

This article is primarily about humans. For other animals, see Animal sexual behaviour. For other uses, see Sex (disambiguation).

"Copulation" redirects here. For copulation among other animals, see Copulation (zoology).

Sexual intercourse in the missionary position depicted by Édouard-Henri Avril (1892)

There are different views on what constitutes sexual intercourse or other sexual activity, which can impact on views on sexual health.[7] Although sexual intercourse, particularly the variant coitus, generally denotes penile–vaginal penetration and the possibility of creating offspring,[1] it also commonly denotes penetrative oral sex and penile–anal sex, especially the latter.[8] It usually encompasses sexual penetration, while non-penetrative sex has been labeled "outercourse",[9] but non-penetrative sex may also be considered sexual intercourse.[4][10] Sex, often a shorthand for sexual intercourse, can mean any form of sexual activity.[7] Because people can be at risk of contracting sexually transmitted infections during these activities, safer sex practices are recommended by health professionals to reduce transmission risk.[11][12]

Various jurisdictions place restrictions on certain sexual acts, such as incest, sexual activity with minors, prostitution, rape, zoophilia, sodomy, premarital and extramarital sex. Religious beliefs also play a role in personal decisions about sexual intercourse or other sexual activity, such as decisions about virginity,[13][14] or legal and public policy matters. Religious views on sexuality vary significantly between different religions and sects of the same religion, though there are common themes, such as prohibition of adultery.

Reproductive sexual intercourse between non-human animals is more often called copulation, and sperm may be introduced into the female's reproductive tract in non-vaginal ways among the animals, such as by cloacal copulation. For most non-human mammals, mating and copulation occur at the point of estrus (the most fertile period of time in the female's reproductive cycle), which increases the chances of successful impregnation.[15][16] However, bonobos, dolphins and chimpanzees are known to engage in sexual intercourse regardless of whether the female is in estrus, and to engage in sex acts with same-sex partners.[17] Like humans engaging in sexual activity primarily for pleasure, this behavior in these animals is also presumed to be for pleasure, and a contributing factor to strengthening their social bonds.[18]

Behaviors

See also: Human sexual activity and Human sexuality

Definitions

19th-century painting of a couple engaged in vaginal intercourse, by Achille Devéria

19th-century erotic interpretation of Roman emperor Hadrian and Antinous engaged in anal intercourse, by Édouard-Henri Avril

Sexual intercourse may be called coitus, copulation, coition, or intercourse. Coitus is derived from the Latin word coitio or coire, meaning "a coming together or joining together" or "to go together", and is known under different ancient Latin names for a variety of sexual activities, but usually denotes penile–vaginal penetration.[19] This is often called vaginal intercourse or vaginal sex.[2][20] Vaginal sex, and less often vaginal intercourse, may also denote any vaginal sexual activity, particularly if penetrative, including sexual activity between lesbian couples.[21][22] Copulation, by contrast, more often denotes the mating process, especially for non-human animals; it can mean a variety of sexual activities between opposite-sex or same-sex pairings,[23] but generally means the sexually reproductive act of transferring sperm from a male to a female or sexual procreation between a man and a woman.[23][24][25]

Although sex and "having sex" also most commonly denote penile–vaginal intercourse,[26] sex can be significantly broad in its meaning and may cover any penetrative or non-penetrative sexual activity between two or more people.[7] The World Health Organization (WHO) states that non-English languages and cultures use different words for sexual activity, "with slightly different meanings".[7] Various vulgarisms, slang, and euphemisms are used for sexual intercourse or other sexual activity, such as fuck, shag, and the phrase "sleep together".[27][28][29] The laws of some countries use the euphemism "carnal knowledge." Penetration of the vagina by the erect penis is additionally known as intromission, or by the Latin name immissio penis (Latin for "insertion of the penis").[30] The age of first sexual intercourse is called sexarche.[31][32]

Vaginal, anal and oral sex are recognized as sexual intercourse more often than other sexual behaviors.[33] Sexual activity that does not involve penile-vaginal sex or other sexual penetration might be used to retain virginity (sometimes called "technical virginity)" or labeled "outercourse".[34] One reason virginity loss is often based on penile–vaginal intercourse is because heterosexual couples may engage in anal or oral sex as a way of being sexually active while maintaining that they are virgins since they have not engaged in the reproductive act of coitus.[35] Some gay men consider frotting or oral sex as a way of maintaining their virginities, with penile-anal penetration used as sexual intercourse and for virginity loss, while other gay men may consider frotting or oral sex as their main forms of sexual activity.[13][36][37] Lesbians may categorize oral sex or fingering as sexual intercourse and subsequently an act of virginity loss,[13][38] or tribadism as a primary form of sexual activity.[39][40]

Researchers commonly use sexual intercourse to denote penile–vaginal intercourse while using specific words, such as anal sex or oral sex, for other sexual behaviors.[41] Scholars Richard M. Lerner and Laurence Steinberg state that researchers also "rarely disclose" how they conceptualize sex "or even whether they resolved potential discrepancies" in conceptualizations of sex.[38] Lerner and Steinberg attribute researchers' focus on penile–vaginal sex to "the larger culture's preoccupation with this form of sexual activity," and have expressed concern that the "widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question [about sexual activity] matches what the researcher had in mind'".[38] This focus can also relegate other forms of mutual sexual activity to foreplay or contribute to them not being regarded as "real sex", and limits the meaning of rape.[42][43] It may also be that conceptually conflating sexual activity with vaginal intercourse and sexual function hinders and limits information about sexual behavior that non-heterosexual people may be engaging in, or information about heterosexuals who may be engaging in non–vaginal sexual activity.[42]

Studies regarding the meaning of sexual intercourse sometimes conflict. While most consider penile–vaginal intercourse to be sex, whether anal or oral intercourse are considered sex is more debatable, with oral sex ranking lowest.[44][45] The Centers for Disease Control and Prevention (CDC) stated that "although there are only limited national data about how often adolescents engage in oral sex, some data suggest that many adolescents who engage in oral sex do not consider it to be 'sex'; therefore they may use oral sex as an option to experience sex while still, in their minds, remaining abstinent".[46] Upton et al. stated, "It is possible that individuals who engage in oral sex, but do not consider it as 'sex', may not associate the acts with the potential health risks they can bring."[44] In other cases, condom use is a factor, with some men stating that sexual activity involving the protection of a condom is not "real sex" or "the real thing".[47][48] This view is common among men in Africa,[47][48] where sexual activity involving the protection of a condom is often associated with emasculation because condoms prevent direct penile–to–skin genital contact.[47]

Stimulation

Sexual intercourse or other sexual activity can encompass various sexually stimulating factors (physiological stimulation or psychological stimulation), including different sex positions (such as the missionary position, the most common human sex position) or the use of sex toys.[49][50] Foreplay may precede some sexual activities, often leading to sexual arousal of the partners and resulting in the erection of the penis or natural lubrication of the vagina.[51] It is also common for people to be as sexually satisfied by being kissed, touched erotically, or held as they are by sexual intercourse.[52]

Non-primate females copulate only when in estrus,[53] but sexual intercourse is possible at any time of the menstrual cycle for women.[54][55] Sex pheromones facilitate copulatory reflexes in various organisms, but, in humans, the detection of pheromones is impaired and they have only residual effects.[56] Non-primate females put themselves in the crucial lordosis position and remain motionless, but these motor copulatory reflexes are no longer functional in women.[53]

Édouard-Henri Avril depiction of a woman on top position, a position that is more likely to stimulate the clitoris[57]

During coitus, the partners orient their hips to allow the penis to move back and forth in the vagina to cause friction, typically without fully removing the penis. In this way, they stimulate themselves and each other, often continuing until orgasm in either or both partners is achieved.[10][58]

For human females, stimulation of the clitoris plays a significant role in sexual activity; 70–80% of women require direct clitoral stimulation to achieve orgasm,[59][60][61] though indirect clitoral stimulation (for example, via vaginal intercourse) may also be sufficient (see orgasm in females).[62][63] Because of this, some couples may engage in the woman on top position or the coital alignment technique, a technique combining the "riding high" variation of the missionary position with pressure-counterpressure movements performed by each partner in rhythm with sexual penetration, to maximize clitoral stimulation.[57][64]

Édouard-Henri Avril depiction of cunnilingus in the life of Sappho

Anal sex involves stimulation of the anus, anal cavity, sphincter valve or rectum; it most commonly means the insertion of a man's penis into another person's rectum, but may also mean the use of sex toys or fingers to penetrate the anus, or oral sex on the anus (anilingus), or pegging.[65]

Oral sex consists of all the sexual activities that involve the use of the mouth and throat to stimulate genitalia or anus. It is sometimes performed to the exclusion of all other forms of sexual activity, and may include the ingestion or absorption of semen (during fellatio) or vaginal fluids (during cunnilingus).[49][66]

Fingering (or digital penetration or digital intercourse) involves the manual manipulation of the clitoris, rest of the vulva, vagina or anus for the purpose of sexual arousal and sexual stimulation; it may constitute the entire sexual encounter or it may be part of mutual masturbation, foreplay or other sexual activities.[22][67][68]

Reproduction

Main articles: Sexual reproduction and Human reproduction

Chance of fertilization by menstrual cycle day relative to ovulation[69]

Natural human reproduction involves penile–vaginal penetration,[70] during which semen, containing male gametes known as sperm cells or spermatozoa, is expelled via ejaculation through the penis into the vagina. The sperm passes through the vaginal vault, cervix and into the uterus, and then into the fallopian tubes. Millions of sperm are present in each ejaculation to increase the chances of fertilization (see sperm competition), but only one reaching an egg or ovum is sufficient to achieve fertilization. When a fertile ovum from the female is present in the fallopian tubes, the male gamete joins with the ovum, resulting in fertilization and the formation of a new embryo. When a fertilized ovum reaches the uterus, it becomes implanted in the lining of the uterus (the endometrium) and a pregnancy begins.[70][71]

Pregnancy rates for sexual intercourse are highest during the menstrual cycle time from some 5 days before until 1 to 2 days after ovulation.[72] For optimal pregnancy chance, there are recommendations of sexual intercourse every 1 or 2 days,[73] or every 2 or 3 days.[74] Studies have shown no significant difference between different sex positions and pregnancy rate, as long as it results in ejaculation into the vagina.[75]

When a sperm donor has sexual intercourse with a woman who is not his partner and for the sole purpose of impregnating the woman, this may be known as natural insemination, as opposed to artificial insemination. Artificial insemination is a form of assisted reproductive technology, which are methods used to achieve pregnancy by artificial or partially artificial means.[76] For artificial insemination, sperm donors may donate their sperm through a sperm bank, and the insemination is performed with the express intention of attempting to impregnate the female; to this extent, its purpose is the medical equivalent of sexual intercourse.[77][78] Reproductive methods also extend to gay and lesbian couples. For gay male pairings, there is the option of surrogate pregnancy; for lesbian couples, there is donor insemination in addition to choosing surrogate pregnancy.[79][80]

Safe sex and birth control

See also: Coitus interruptus

There are a variety of safe sex methods that are practiced by heterosexual and same-sex couples, including non-penetrative sex acts,[12][81] and heterosexual couples may use oral or anal sex (or both) as a means of birth control.[82][83] However, pregnancy can still occur with anal sex or other forms of sexual activity if the penis is near the vagina (such as during intercrural sex or other genital-genital rubbing) and its sperm is deposited near the vagina's entrance and travels along the vagina's lubricating fluids; the risk of pregnancy can also occur without the penis being near the vagina because sperm may be transported to the vaginal opening by the vagina coming in contact with fingers or other non-genital body parts that have come in contact with semen.[84][85]

Safe sex is a relevant harm reduction philosophy[86] and condoms are used as a form of safe sex and contraception. Condoms are widely recommended for the prevention of sexually transmitted infections (STIs).[86] According to reports by the National Institutes of Health (NIH) and World Health Organization (WHO), correct and consistent use of latex condoms reduces the risk of HIV/AIDS transmission by approximately 85–99% relative to risk when unprotected.[87][88] Condoms are rarely used for oral sex and there is significantly less research on behaviors with regard to condom use for anal and oral sex.[89] The most effective way to avoid sexually transmitted infections is to abstain from sexual intercourse, especially vaginal, anal, and oral sexual intercourse.[86]

Decisions and options concerning birth control can be affected by cultural reasons, such as religion, gender roles or folklore.[90] In the predominantly Catholic countries Ireland, Italy and the Philippines, fertility awareness and the rhythm method are emphasized while disapproval is expressed with regard to other contraceptive methods.[11] Worldwide, sterilization is a more common birth control method,[11] and use of the intrauterine device (IUD) is the most common and effective way of reversible contraception.[11][91] Conception and contraception are additionally a life-and-death situation in developing countries, where one in three women give birth before age 20; however, 90% of unsafe abortions in these countries could be prevented by effective contraception use.[11]

The National Survey of Sexual Health and Behavior (NSSHB) indicated in 2010 that "1 of 4 acts of vaginal intercourse are condom-protected in the U.S. (1 in 3 among singles)," that "condom use is higher among black and Hispanic Americans than among white Americans and those from other racial groups," and that "adults using a condom for intercourse were just as likely to rate the sexual extent positively in terms of arousal, pleasure and orgasm than when having intercourse without one".[92]

Prevalence

"Coition of a Hemisected Man and Woman" (c. 1492), an interpretation of what happens inside the body during coitus, by Leonardo da Vinci

Penile–vaginal penetration is the most common form of sexual intercourse.[2][20] Studies indicate that most heterosexual couples engage in vaginal intercourse nearly every sexual encounter.[20] The National Survey of Sexual Health and Behavior (NSSHB) reported in 2010 that vaginal intercourse is "the most prevalent sexual behavior among men and women of all ages and ethnicities".[20] Clint E. Bruess et al. stated that it "is the most frequently studied behavior" and is "often the focus of sexuality education programming for youth."[93] Weiten et al. said that it "is the most widely endorsed and practiced sexual act in our society."[40]

Regarding oral or anal intercourse, the CDC stated in 2009, "Studies indicate that oral sex is commonly practiced by sexually active male-female and same-gender couples of various ages, including adolescents."[46] Oral sex is significantly more common than anal sex.[40][45] The 2010 NSSHB study reported that vaginal intercourse was practiced more than insertive anal intercourse among men, but that 13% to 15% of men aged 25 to 49 practiced insertive anal intercourse. Receptive anal intercourse was infrequent among men, with approximately 7% of men aged 14 to 94 years old having said that they were a receptive partner during anal intercourse. It said that women engage in anal intercourse less commonly than men, but that the practice is not uncommon among women; it was estimated that 10% to 14% of women aged 18 to 39 years old practiced anal sex in the past 90 days, and that most of the women said they practiced it once a month or a few times a year.[20]

Age at first intercourse

The prevalence of sexual intercourse has been compared cross-culturally. In 2003, Michael Bozon of the French Institut national d'études démographiques conducted a cross-cultural study titled "At what age do women and men have their first sexual intercourse?" In the first group of the contemporary cultures he studied, which included sub-Saharan Africa (listing Mali, Senegal and Ethiopia), the data indicated that the age of men at sexual initiation in these societies is at later ages than that of women, but is often extra-marital; the study considered the Indian subcontinent to also fall into this group, though data was only available from Nepal.[94][95]

In the second group, the data indicated families encouraged daughters to delay marriage, and to abstain from sexual activity before that time. However, sons are encouraged to gain experience with older women or prostitutes before marriage. Age of men at sexual initiation in these societies is at lower ages than that of women; this group includes south European and Latin cultures (Portugal, Greece and Romania are noted) and such from Latin America (Brazil, Chile, and the Dominican Republic). The study considered many Asian societies to also fall into this group, although matching data was only available from Thailand.[94][95]

In the third group, age of men and women at sexual initiation was more closely matched; there were two sub-groups, however. In non-Latin, Catholic countries (Poland and Lithuania are mentioned), age at sexual initiation was higher, suggesting later marriage and reciprocal valuing of male and female virginity. The same pattern of late marriage and reciprocal valuing of virginity was reflected in Singapore and Sri Lanka. The study considered China and Vietnam to also fall into this group, though data were not available.[94][95] In northern and eastern European countries, age at sexual initiation was lower, with both men and women involved in sexual intercourse before any union formation; the study listed Switzerland, Germany and the Czech Republic as members of this group.[94][95]

Concerning United States data, tabulations by the National Center for Health Statistics report that the age of first sexual intercourse was 17.1 years for both males and females in 2010.[96] The CDC stated that 45.5 percent of girls and 45.7 percent of boys had engaged in sexual activity by 19 in 2002; in 2011, reporting their research from 2006–2010, they stated that 43% of American unmarried teenage girls and 42% of American unmarried teenage boys have ever engaged in sexual intercourse.[97] The CDC also reports that American girls will most likely lose their virginity to a boy who is 1 to 3 years older than they are.[97] Between 1988 and 2002, the percentage of people in the U.S. who had sexual intercourse between the ages of 15 to 19 fell from 60 to 46 percent for never-married males, and from 51 to 46 percent for never-married females.[98]

Health effects

Benefits

In humans, sexual intercourse and sexual activity in general have been reported as having health benefits as varied as increased immunity by increasing the body's production of antibodies and subsequent lower blood pressure,[99][100] and decreased risk of prostate cancer.[99] Sexual intimacy and orgasms increase levels of the hormone oxytocin (also known as "the love hormone"), which can help people bond and build trust.[100][101] Oxytocin is believed to have a more significant impact on women than on men, which may be why women associate sexual attraction or sexual activity with romance and love more than men do.[6] A long-term study of 3,500 people between ages 18 and 102 by clinical neuropsychologist David Weeks indicated that, based on impartial ratings of the subjects' photographs, sex on a regular basis helps people look significantly chronologically younger.[102]

Risks

Sexually transmitted infections (STIs) are bacteria, viruses or parasites that are spread by sexual contact, especially vaginal, anal, or oral intercourse, or unprotected sex.[103][104] Oral sex is less risky than vaginal or anal intercourse.[105] Many times, STIs initially do not cause symptoms, increasing the risk of unknowingly passing the infection on to a sex partner or others.[106][107]

There are 19 million new cases of sexually transmitted infections every year in the U.S.,[108] and, in 2005, the World Health Organization (WHO) estimated that 448 million people aged 15–49 were infected per year with curable STIs (such as syphilis, gonorrhea and chlamydia).[109] Some STIs can cause a genital ulcer; even if they do not, they increase the risk of both acquiring and passing on HIV up to ten-fold.[109] Hepatitis B can also be transmitted through sexual contact.[110] Globally, there are about 257 million chronic carriers of hepatitis B.[111] HIV is one of the world's leading infectious killers; in 2010, approximately 30 million people were estimated to have died because of it since the beginning of the epidemic. Of the 2.7 million new HIV infections estimated to occur worldwide in 2010, 1.9 million (70%) were in Africa. The World Health Organization also stated that the "estimated 1.2 million Africans who died of HIV-related illnesses in 2010 comprised 69% of the global total of 1.8 million deaths attributable to the epidemic."[112] It is diagnosed by blood tests, and while no cure has been found, it can be controlled by management through antiretroviral drugs for the disease, and patients can enjoy healthy and productive lives.[113]

In cases where infection is suspected, early medical intervention is highly beneficial in all cases. The CDC stated "the risk of HIV transmission from an infected partner through oral sex is much less than the risk of HIV transmission from anal or vaginal sex," but that "measuring the exact risk of HIV transmission as a result of oral sex is very difficult" and that this is "because most sexually active individuals practice oral sex in addition to other forms of sex, such as vaginal and/or anal sex, when transmission occurs, it is difficult to determine whether it occurred as a result of oral sex or other more risky sexual activities". They added that "several co-factors may increase the risk of HIV transmission through oral sex"; this includes ulcers, bleeding gums, genital sores, and the presence of other STIs.[46]

In 2005, the World Health Organization estimated that 123 million women become pregnant worldwide each year, and around 87 million of those pregnancies or 70.7% are unintentional. Approximately 46 million pregnancies per year reportedly end in induced abortion.[114] Approximately 6 million U.S. women become pregnant per year. Out of known pregnancies, two-thirds result in live births and roughly 25% in abortions; the remainder end in miscarriage. However, many more women become pregnant and miscarry without even realizing it, instead mistaking the miscarriage for an unusually heavy menstruation.[115] The U.S. teenage pregnancy rate fell by 27 percent between 1990 and 2000, from 116.3 pregnancies per 1,000 girls aged 15–19 to 84.5. This data includes live births, abortions, and fetal losses. Almost 1 million American teenage women, 10% of all women aged 15–19 and 19% of those who report having had intercourse, become pregnant each year.[116]

Sexual activity can increase the expression of a gene transcription factor called ΔFosB (delta FosB) in the brain's reward center;[117][118][119] consequently excessively frequent engagement in sexual activity on a regular (daily) basis can lead to the overexpression of ΔFosB, inducing an addiction to sexual activity.[117][118][119] Sexual addiction or hypersexuality is often considered an impulse control disorder or a behavioral addiction. It has been linked to atypical levels of dopamine, a neurotransmitter. This behavior is characterized by a fixation on sexual intercourse and disinhibition. It was proposed that this 'addictive behavior' be classified in DSM-5 as an impulsive–compulsive behavioral disorder. Addiction to sexual intercourse is thought to be genetically linked. Those having an addiction to sexual intercourse have a higher response to visual sexual cues in the brain. Those seeking treatment will typically see a physician for pharmacological management and therapy.[120] One form of hypersexuality is Kleine–Levin syndrome. It is manifested by hypersomnia and hypersexuality and remains relatively rare.[121]

Sexual activity can directly cause death, particularly due to coronary circulation complications, which is sometimes called coital death, coital sudden death or coital coronary.[10][122][123] However, coital deaths are significantly rare.[122] People, especially those who get little or no physical exercise, have a slightly increased risk of triggering a heart attack or sudden cardiac death when they engage in sexual intercourse or any vigorous physical exercise that is engaged in on a sporadic basis.[123] Regular exercise reduces, but does not eliminate, the increased risk.[123]

Duration and genital complications

See also: Intravaginal ejaculation latency time and Coitus reservatus

Sexual intercourse, when involving a male participant, often ends when the male has ejaculated, and thus the partner might not have time to reach orgasm.[124] In addition, premature ejaculation (PE) is common, and women often require a substantially longer duration of stimulation with a sexual partner than men do before reaching an orgasm.[51][125][126] Scholars, such as Weiten et al., state that "many couples are locked into the idea that orgasms should be achieved only through intercourse [penile-vaginal sex]," that "the word foreplay suggests that any other form of sexual stimulation is merely preparation for the 'main event'" and that "because women reach orgasm through intercourse less consistently than men," they are likelier than men to fake an orgasm to satisfy their sexual partners.[51]

Painting of an Indian couple (a prince and lady) prolonging sexual intercourse

In 1991, scholars from the Kinsey Institute stated, "The truth is that the time between penetration and ejaculation varies not only from man to man, but from one time to the next for the same man." They added that the appropriate length for sexual intercourse is the length of time it takes for both partners to be mutually satisfied, emphasizing that Kinsey "found that 75 percent of men ejaculated within two minutes of penetration. But he didn't ask if the men or their partners considered two minutes mutually satisfying" and "more recent research reports slightly longer times for intercourse".[127] A 2008 survey of Canadian and American sex therapists stated that the average time for heterosexual intercourse (coitus) was 7 minutes and that 1 to 2 minutes was too short, 3 to 7 minutes was adequate and 7 to 13 minutes desirable, while 10 to 30 minutes was too long.[20][128]

Anorgasmia is regular difficulty reaching orgasm after ample sexual stimulation, causing personal distress.[129] This is significantly more common in women than in men,[130][131] which has been attributed to the lack of sex education with regard to women's bodies, especially in sex-negative cultures, such as clitoral stimulation usually being key for women to orgasm.[131] The physical structure of coitus favors penile stimulation over clitoral stimulation; the location of the clitoris then usually necessitates manual or oral stimulation in order for the woman to achieve orgasm.[51] Approximately 25% of women report difficulties with orgasm,[20] 10% of women have never had an orgasm,[132] and 40% or 40–50% have either complained about sexual dissatisfaction or experienced difficulty becoming sexually aroused at some point in their lives.[133]

Vaginismus is involuntary tensing of the pelvic floor musculature, making coitus, or any form of penetration of the vagina, distressing, painful and sometimes impossible for women. It is a conditioned reflex of the pubococcygeus muscle, and is sometimes referred to as the PC muscle. Vaginismus can be hard to overcome because if a woman expects to experience pain during sexual intercourse, this can cause a muscle spasm, which results in painful sexual intercourse.[131][134] Treatment of vaginismus often includes both psychological and behavioral techniques, including the use of vaginal dilators.[135] Additionally, the use of Botox as a medical treatment for vaginismus has been tested and administered.[136] Painful or uncomfortable sexual intercourse may also be categorized as dyspareunia.[135]

Approximately 40% of males reportedly suffer from some form of erectile dysfunction (ED) or impotence, at least occasionally.[137] Premature ejaculation has been reported to be more common than erectile dysfunction, although some estimates suggest otherwise.[125][126][137] Due to various meanings of the disorder, estimates for the prevalence of premature ejaculation vary significantly more than for erectile dysfunction.[125][126] For example, the Mayo Clinic states, "Estimates vary, but as many as 1 out of 3 men may be affected by [premature ejaculation] at some time."[138] Further, "Masters and Johnson speculated that premature ejaculation is the most common sexual dysfunction, even though more men seek therapy for erectile difficulties" and that this is because "although an estimated 15 percent to 20 percent of men experience difficulty controlling rapid ejaculation, most do not consider it a problem requiring help, and many women have difficulty expressing their sexual needs".[127] The American Urological Association (AUA) estimates that premature ejaculation could affect 21 percent of men in the United States.[139]

For those whose impotence is caused by medical conditions, prescription drugs such as Viagra, Cialis, and Levitra are available. However, doctors caution against the unnecessary use of these drugs because they are accompanied by serious risks such as increased chance of heart attack.[140] The selective serotonin reuptake inhibitor (SSRI) and antidepressant drug dapoxetine has been used to treat premature ejaculation.[141] In clinical trials, those with PE who took dapoxetine experienced sexual intercourse three to four times longer before orgasm than without the drug.[142] Another ejaculation-related disorder is delayed ejaculation, which can be caused as an unwanted side effect of antidepressant medications such as fluvoxamine; however, all SSRIs have ejaculation-delaying effects, and fluvoxamine has the least ejaculation-delaying effects.[143]

Sexual intercourse remains possible after major medical treatment of the reproductive organs and structures. This is especially true for women. Even after extensive gynecological surgical procedures (such as hysterectomy, oophorectomy, salpingectomy, dilation and curettage, hymenotomy, Bartholin gland surgery, abscess removal, vestibulectomy, labia minora reduction, cervical conization, surgical and radiological cancer treatments and chemotherapy), coitus can continue. Reconstructive surgery remains an option for women who have experienced benign and malignant conditions.[144]

Disabilities and other complications

Main article: Sexuality and disability

Obstacles that those with disabilities face with regard to engaging in sexual intercourse include pain, depression, fatigue, negative body image, stiffness, functional impairment, anxiety, reduced libido, hormonal imbalance, and drug treatment or side effects. Sexual functioning has been regularly identified as a neglected area of the quality of life in patients with rheumatoid arthritis.[145] For those that must take opioids for pain control, sexual intercourse can become more difficult.[146] Having a stroke can also largely impact on the ability to engage in sexual intercourse.[147] Although disability-related pain, including as a result of cancer, and mobility impairment can hamper sexual intercourse, in many cases, the most significant impediments to sexual intercourse for individuals with a disability are psychological.[148] In particular, people who have a disability can find sexual intercourse daunting due to issues involving their self-concept as a sexual being, or a partner's discomfort or perceived discomfort.[148] Temporary difficulties can arise with alcohol and sex, as alcohol can initially increase interest through disinhibition but decrease capacity with greater intake; however, disinhibition can vary depending on the culture.[149][150]

The mentally disabled also are subject to challenges in participating in sexual intercourse. Women with Intellectual disabilities (ID) are often presented with situations that prevent sexual intercourse. This can include the lack of a knowledgeable healthcare provider trained and experienced in counseling those with ID on sexual intercourse. Those with ID may have hesitations regarding the discussion of the topic of sex, a lack of sexual knowledge and limited opportunities for sex education. In addition there are other barriers such as a higher prevalence of sexual abuse and assault. These crimes often remain underreported. There remains a lack of "dialogue around this population's human right to consensual sexual expression, undertreatment of menstrual disorders, and legal and systemic barriers". Women with ID may lack sexual health care and sex education. They may not recognize sexual abuse. Consensual sexual intercourse is not always an option for some. Those with ID may have limited knowledge and access to contraception, screening for sexually transmitted infections and cervical cancer.[151]

Social effects

See also: Human mating strategies and Pair bond

Adults

Sexual intercourse may be for reproductive, relational, or recreational purposes.[152] It often plays a strong role in human bonding.[6] In many societies, it is normal for couples to have sexual intercourse while using some method of birth control, sharing pleasure and strengthening their emotional bond through sexual activity even though they are deliberately avoiding pregnancy.[6]

In humans and bonobos, the female undergoes relatively concealed ovulation so that male and female partners commonly do not know whether she is fertile at any given moment. One possible reason for this distinct biological feature may be formation of strong emotional bonds between sexual partners important for social interactions and, in the case of humans, long-term partnership rather than immediate sexual reproduction.[54]

Sexual dissatisfaction due to the lack of sexual intercourse is associated with increased risk of divorce and relationship dissolution, especially for men.[153][154][155] Some research, however, indicates that general dissatisfaction with marriage for men results if their wives flirted with, erotically kissed or became romantically or sexually involved with another man (infidelity),[153][154] and that this is especially the case for men with a lower emotional and composite marital satisfaction.[155] Other studies report that the lack of sexual intercourse does not significantly result in divorce, though it is commonly one of the various contributors to it.[156][157] According to the 2010 National Survey of Sexual Health and Behavior (NSSHB), men whose most recent sexual encounter was with a relationship partner reported greater arousal, greater pleasure, fewer problems with erectile function, orgasm, and less pain during the event than men whose last sexual encounter was with a non-relationship partner.[158]

For women, there is often a complaint about the lack of their spouses' sexual spontaneity. Decreased sexual activity among these women may be the result of their perceived failure to maintain ideal physical attractiveness or because their sexual partners' health issues have hindered sexual intercourse.[159] Some women express that their most satisfying sexual experiences entail being connected to someone, rather than solely basing satisfaction on orgasm.[124][160] With regard to divorce, women are more likely to divorce their spouses for a one-night stand or various infidelities if they are in less cooperative or high-conflict marriages.[155]

Research additionally indicates that non-married couples who are cohabiting engage in sexual intercourse more often than married couples, and are more likely to participate in sexual activity outside of their sexual relationships; this may be due to the "honeymoon" effect (the newness or novelty of sexual intercourse with the partner), since sexual intercourse is usually practiced less the longer a couple is married, with couples engaging in sexual intercourse or other sexual activity once or twice a week, or approximately six to seven times a month.[161] Sexuality in older age also affects the frequency of sexual intercourse, as older people generally engage in sexual intercourse less frequently than younger people do.[161]

Adolescents

Main article: Adolescent sexuality

Adolescents commonly use sexual intercourse for relational and recreational purposes, which may negatively or positively impact their lives. For example, while teenage pregnancy may be welcomed in some cultures, it is also commonly disparaged, and research suggests that the earlier onset of puberty for children puts pressure on children and teenagers to act like adults before they are emotionally or cognitively ready.[162] Some studies have concluded that engaging in sexual intercourse leaves adolescents, especially girls, with higher levels of stress and depression, and that girls may be likelier to engage in sexual risk (such as sexual intercourse without the use of a condom),[163][164] but it may be that further research is needed in these areas.[164] In some countries, such as the United States, sex education and abstinence-only sex education curricula are available to educate adolescents about sexual activity; these programs are controversial, as debate exists as to whether teaching children and adolescents about sexual intercourse or other sexual activity should only be left up to parents or other caregivers.[165]

Some studies from the 1970s through 1990s suggested an association between self-esteem and sexual intercourse among adolescents,[166] while other studies, from the 1980s and 1990s, reported that the research generally indicates little or no relationship between self-esteem and sexual activity among adolescents.[167] By the 1990s, the evidence mostly supported the latter,[167] and further research has supported little or no relationship between self-esteem and sexual activity among adolescents.[168][169] Scholar Lisa Arai stated, "The idea that early sexual activity and pregnancy is linked to low self-esteem became fashionable in the latter half of the 20th century, particularly in the US," adding that, "Yet, in a systematic review of the relationship between self-esteem and teenagers' sexual behaviours, attitudes and intentions (which analyzed findings from 38 publications) 62% of behavioral findings and 72% of the attitudinal findings exhibited no statistically significant associations (Goodson et al, 2006)."[169] Studies that do find a link suggest that non-virgin boys have higher self-esteem than virgin boys and that girls who have low self-esteem and poor self-image are more prone to risk-taking behaviors, such as unprotected sex and multiple sexual partners.[166][168][169]

Psychiatrist Lynn Ponton wrote, "All adolescents have sex lives, whether they are sexually active with others, with themselves, or seemingly not at all", and that viewing adolescent sexuality as a potentially positive experience, rather than as something inherently dangerous, may help young people develop healthier patterns and make more positive choices regarding sexual activity.[162] Researchers state that long-term romantic relationships allow adolescents to gain the skills necessary for high-quality relationships later in life.[170] Overall, positive romantic relationships among adolescents can result in long-term benefits. High-quality romantic relationships are associated with higher commitment in early adulthood,[171] and are positively associated with social competence.[172][173]

Ethical, religious, and legal views

General

See also: Sexual ethics, Religion and sexuality, and Sex and the law

Erotic painting on ancient Greek kylix

While sexual intercourse, as coitus, is the natural mode of reproduction for the human species, humans have intricate moral and ethical guidelines which regulate the practice of sexual intercourse and vary according to religious and governmental laws. Some governments and religions also have strict designations of "appropriate" and "inappropriate" sexual behavior, which include restrictions on the types of sex acts which are permissible. A historically prohibited or regulated sex act is anal sex.[174][175]

Sexual offenses

Sexual intercourse with a person against their will, or without their consent, is rape, but may also be called sexual assault; it is considered a serious crime in most countries.[176][177] More than 90% of rape victims are female, 99% of rapists male, and only about 5% of rapists are strangers to the victims.[177]

Most countries have age of consent laws which set the minimum legal age with whom an older person may engage in sexual intercourse, usually set at 16 to 18, but ranges from 12 to 20, years of age. In some societies, an age of consent is set by non-statutory custom or tradition.[178] Sex with a person under the age of consent, regardless of their stated consent, is often considered sexual assault or statutory rape depending on differences in ages of the participants. Some countries treat any sex with a person of diminished or insufficient mental capacity to give consent, regardless of age, as rape.[179]

Max Slevogt depiction of rape

Robert Francoeur et al. stated that "prior to the 1970s, rape definitions of sex often included only penile-vaginal sexual intercourse."[180] Authors Pamela J. Kalbfleisch and Michael J. Cody stated that this made it so that if "sex means penile-vaginal intercourse, then rape means forced penile-vaginal intercourse, and other sexual behaviors – such as fondling a person's genitals without her or his consent, forced oral sex, and same-sex coercion – are not considered rape"; they stated that "although some other forms of forced sexual contact are included within the legal category of sodomy (e.g., anal penetration and oral-genital contact), many unwanted sexual contacts have no legal grounding as rape in some states".[43] Ken Plumber argued that the legal meaning "of rape in most countries is unlawful sexual intercourse which means the penis must penetrate the vagina" and that "other forms of sexual violence towards women such as forced oral sex or anal intercourse, or the insertion of other objects into the vagina, constitute the 'less serious' crime of sexual assault".[181]

Over time, the meaning of rape broadened in some parts of the world to include many types of sexual penetration, including anal intercourse, fellatio, cunnilingus, and penetration of the genitals or rectum by an inanimate object.[180] Until 2012, the Federal Bureau of Investigation (FBI) still considered rape a crime solely committed by men against women. In 2012, they changed the meaning from "The carnal knowledge of a female forcibly and against her will" to "The penetration, no matter how slight, of the vagina or anus with any body part or object, or oral penetration by a sex organ of another person, without the consent of the victim." The meaning does not change federal or state criminal codes or impact charging and prosecution on the federal, state or local level, but instead assures that rape will be more accurately reported nationwide.[182][183] In some instances, penetration is not required for the act to be categorized as rape.[184]

In most societies around the world, the concept of incest exists and is criminalized. James Roffee, a senior lecturer in criminology at Monash University,[185] addressed potential harm associated with familial sexual activity, such as resulting children born with deficiencies. However, the law is more concerned with protecting the rights of people who are potentially subjected to such abuse. This is why familial sexual relationships are criminalized, even if all parties are consensual. There are laws prohibiting all kinds of sexual activity between relatives, not necessarily penetrative sex. These laws refer to grandparents, parents, children, siblings, aunts and uncles. There are differences between states in terms of the severity of punishments and what they consider to be a relative, including biological parents, step-parents, adoptive parents and half-siblings.[186]

Another sexual matter concerning consent is zoophilia, which is a paraphilia involving sexual activity between human and non-human animals, or a fixation on such practice.[187][188][189] Human sexual activity with non-human animals is not outlawed in some jurisdictions, but it is illegal in others under animal abuse laws or laws dealing with crimes against nature.[190]

Romantic relationships

Lawrence Alma-Tadema depiction of courtship and a marriage proposal

Marriage and relationships

Sexual intercourse has traditionally been considered an essential part of a marriage, with many religious customs requiring consummation of the marriage and citing marriage as the most appropriate union for sexual reproduction (procreation).[191] In such cases, a failure for any reason to consummate the marriage would be considered a ground for annulment (which does not require a divorce process). Sexual relations between marriage partners have been a "marital right" in various societies and religions, both historically and in modern times, especially with regard to a husband's rights to his wife.[192][193][194] Until the late 20th century, there was usually a marital exemption in rape laws which precluded a husband from being prosecuted under the rape law for forced sex with his wife.[195] Author Oshisanya, 'lai Oshitokunbo stated, "As the legal status of women has changed, the concept of a married man's or woman's marital right to sexual intercourse has become less widely held."[196]

Adultery (engaging in sexual intercourse with someone other than one's spouse) has been, and remains, a criminal offense in some jurisdictions.[197][198] Sexual intercourse between unmarried partners and cohabitation of an unmarried couple are also illegal in some jurisdictions.[199][200] Conversely, in other countries, marriage is not required, socially or legally, in order to have sexual intercourse or to procreate (for example, the majority of births are outside of marriage in countries such as Iceland, Norway, Sweden, Denmark, Bulgaria, Estonia, Slovenia, France, Belgium).[201]

With regard to divorce laws, the refusal to engage in sexual intercourse with one's spouse may give rise to a grounds for divorce, which may be listed under "grounds of abandonment".[202] Concerning no-fault divorce jurisdictions, author James G. Dwyer stated that no-fault divorce laws "have made it much easier for a woman to exit a marital relationship, and wives have obtained greater control over their bodies while in a marriage" because of legislative and judicial changes regarding the concept of a marital exemption when a man rapes his wife.[192]

There are various legal positions regarding the meaning and legality of sexual intercourse between persons of the same sex or gender. For example, in the 2003 New Hampshire Supreme Court case Blanchflower v. Blanchflower, it was held that female same-sex sexual relations, and same-sex sexual practices in general, did not constitute sexual intercourse, based on a 1961 entry in Webster's Third New International Dictionary that categorizes sexual intercourse as coitus; and thereby an accused wife in a divorce case was found not guilty of adultery.[203][204] Some countries consider same-sex sexual behavior an offense punishable by imprisonment or execution; this is the case, for example, in Islamic countries, including LGBT issues in Iran.[205][206]

Opposition to same-sex marriage is largely based on the belief that sexual intercourse and sexual orientation should be of a heterosexual nature.[207][208][209] The recognition of such marriages is a civil rights, political, social, moral and religious issue in many nations, and the conflicts arise over whether same-sex couples should be allowed to enter into marriage, be required to use a different status (such as a civil union, which either grant equal rights as marriage or limited rights in comparison to marriage), or not have any such rights. A related issue is whether the word marriage should be applied.[208][209]

Religious views

See also: Religion and sexuality

There are wide differences in religious views with regard to sexual intercourse in or outside of marriage:

• Most denominations of Christianity, including Catholicism, have strict views or rules on what sexual practices are and are not acceptable.[210] Most Christian views on sexual intercourse are influenced by various interpretations of the Bible.[211] Sexual intercourse outside of marriage, for example, is considered a sin in some churches; in such cases, sexual intercourse may be called a sacred covenant, holy, or a holy sacrament between husband and wife.[210][211] Historically, Christian teachings often promoted celibacy,[212] although today usually only certain members (for example, certain religious leaders) of some groups take a vow of celibacy, forsaking both marriage and any type of sexual or romantic activity.[211] The Bible may be interpreted as endorsing penile-vaginal penetration as the only form of acceptable sexual activity,[213][214] while other interpretations view the Bible as not being clear on oral sex or other particular sexual behaviors and that it is a personal decision as to whether oral sex is acceptable within marriage.[213][215][216] Some sects consider the use of birth control to prevent sexual reproduction a grave sin against God and marriage, as they believe that the main purpose of marriage, or one of its primary purposes, is to produce children, while other sects do not hold such beliefs.[217] The Bible also prohibits sexual intercourse during menstruation.[216]
  • In the Roman Catholic Church, if a matrimonial celebration takes place (ratification), but the spouses have not yet engaged in intercourse (consummation), then the marriage is considered to be a marriage via ratum sed non consummatum. Such a marriage, regardless of the reason for non-consummation, can be dissolved by the pope.[218]
  • In The Church of Jesus Christ of Latter-day Saints (LDS Church) sexual relations within the bonds of matrimony are seen as sacred. Latter-day Saints consider sexual relations to be ordained of God for the creation of children and for the expression of love between husband and wife. Members are discouraged from having any sexual relations before marriage, and from being unfaithful to their spouses after marriage.[219]
  • Shakers believe that sexual intercourse is the root of all sin and that all people should therefore be celibate, including married couples. The original Shaker community that peaked at 6,000 full members in 1840 dwindled to three members by 2009.[220]
• In Judaism, a married Jewish man is required to provide his wife with sexual pleasure called onah (literally, "her time"), which is one of the conditions he takes upon himself as part of the Jewish marriage contract, ketubah, that he gives her during the Jewish wedding ceremony. In Jewish views on marriage, sexual desire is not evil, but must be satisfied in the proper time, place and manner.[221]
• Islam views sex within marriage as something pleasurable, a spiritual activity, and a duty.[222][223][224] Muslim men, both Sunni and Shia, are allowed to marry permanently up to four women. In Shia Islam, men are allowed to enter into an unlimited number of temporary marriages, which are contracted to last for a period of minutes to multiple years and permit sexual intercourse. Sunni women are allowed to enter only one marriage permanently at a time whereas Shia women both temporary or permanent. Sex outside of marriage (including adultery and fornication), homosexual behavior, and engaging in anal sex are prohibited, and this is commonly defined as zina.[225][226][227]
• Hinduism has varied views about sexuality, but Hindu society, in general, perceives extramarital sex to be immoral and shameful.[222]…Hindu society, in general, perceives extramarital sex to be immoral and shameful.
• Buddhist ethics, in its most general formulation, holds that one should neither be attached to nor crave sensual pleasure since it binds one to the cycle of birth and death, samsara, and prevents one attaining the goal of Nirvana. Since Buddhist monastics (i.e. bhikshus and bhikshunis) are to be fully dedicated towards this goal, they undertake the training rule of total abstinence from sexual intercourse, i.e. of celibacy. Other monastic training rules from the Code of Discipline (Patimokkha or Pratimoksasutra) and canonical Vinaya scriptures are to prevent masturbation, lustfully touching and speaking to members of the other sex, and other forms of sexual behaviour. Buddhist lay people undertake the Five Precepts, the third of which is avoiding sexual misconduct. Peter Harvey says that this precept "relates primarily to the avoidance of causing suffering by one's sexual behaviour. Adultery—'going with the wife of another'—is the most straightforward breach of this precept. The wrongness of this is seen as partly in terms of its being an expression of greed, and partly in terms of its harm to others. It is said that a man breaks the precept if he has intercourse with women who are engaged, or who are still protected by any relative, or young girls not protected by a relative, Clearly, rape and incest are breaches of the precept."[228] The Buddhist Canonical scriptures contain no other regulations or recommendations for lay people—for example, with regards homosexuality, masturbation, sexual practices and contraceptives. However, in keeping with the Buddhist ethical principles of not-harming and avoiding shame, guilt and remorse, socially taboo forms of sexuality as well as obsessive sexual activities can also be seen as being included in the third precept. Later Buddhist authors such as Nagarjuna give various clarifications and recommendations.[229]
• In the Bahá'í Faith, sexual relationships are permitted only between a husband and wife.[230]
• Unitarian Universalists, with an emphasis on strong interpersonal ethics, do not place boundaries on the occurrence of sexual intercourse among consenting adults.[231]
• According to the Brahma Kumaris and Prajapita Brahma Kumaris religion, the power of lust is the root of all evil and worse than murder.[232] Purity (celibacy) is promoted for peace and to prepare for life in forthcoming Heaven on earth for 2,500 years when children will be created by the power of the mind.[233][234]
• Wiccans are told, as declared within the Charge of the Goddess, to "[l]et [the Goddess'] worship be within the heart that rejoiceth; for behold, all acts of love and pleasure are [the Goddess'] rituals." This statement appears to allow one freedom to explore sensuality and pleasure, and mixed with the final maxim within the Wiccan Rede—"26. Eight words the Wiccan Rede fulfill—an' it harm none, do what ye will."[235]—Wiccans are encouraged to be responsible with their sexual encounters, in whatever variety they may occur.[236]
• Meher Baba maintained that "In the beginning of married life the partners are drawn to each other by lust as well as love; but with conscious and deliberate cooperation they can gradually lessen the element of lust and increase the element of love. Through this process of sublimation, lust ultimately gives place to deep love."[237]

In some cases, the sexual intercourse between two people is seen as counter to religious law or doctrine. In many religious communities, including the Catholic Church and Mahayana Buddhists, religious leaders are expected to refrain from sexual intercourse in order to devote their full attention, energy, and loyalty to their religious duties.[238]

Other animals

Main articles: Copulation (zoology) and Animal sexual behaviour

A pair of lions copulating in the Maasai Mara, Kenya

Mating houseflies

In zoology, copulation often means the process in which a male introduces sperm into the female's body, especially directly into her reproductive tract.[15][24] Spiders have separate male and female sexes. Before mating and copulation, the male spider spins a small web and ejaculates on to it. He then stores the sperm in reservoirs on his large pedipalps, from which he transfers sperm to the female's genitals. The females can store sperm indefinitely.[239]

Many animals that live in water use external fertilization, whereas internal fertilization may have developed from a need to maintain gametes in a liquid medium in the Late Ordovician epoch. Internal fertilization with many vertebrates (such as reptiles, some fish, and most birds) occur via cloacal copulation (see also hemipenis), while mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization.[240][241]

For primitive insects, the male deposits spermatozoa on the substrate, sometimes stored within a special structure; courtship involves inducing the female to take up the sperm package into her genital opening, but there is no actual copulation.[242][243] In groups that have reproduction similar to spiders, such as dragonflies, males extrude sperm into secondary copulatory structures removed from their genital opening, which are then used to inseminate the female. In dragonflies, it is a set of modified sternites on the second abdominal segment.[244] In advanced groups of insects, the male uses its aedeagus, a structure formed from the terminal segments of the abdomen, to deposit sperm directly (though sometimes in a capsule called a spermatophore) into the female's reproductive tract.[245]

Bonobos, chimpanzees and dolphins are species known to engage in heterosexual behaviors even when the female is not in estrus, which is a point in her reproductive cycle suitable for successful impregnation. These species are also known to engage in same-sex sexual behaviors.[17] In these animals, the use of sexual intercourse has evolved beyond reproduction to apparently serve additional social functions (such as bonding).[18]

See also

• Human sexual response cycle

References

1. Sexual intercourse most commonly means penile–vaginal penetration for sexual pleasure and/or sexual reproduction; dictionary sources state that it especially means this, and scholarly sources over the years agree. See, for example;
   • "Sexual intercourse". Dictionary.com. Retrieved November 22, 2019.
   • "Sexual intercourse". Merriam-Webster. Retrieved December 5, 2014.
   • "Sexual intercourse". Macmillandictionary.com. Retrieved May 9, 2019.
   • Richard M. Lerner; Laurence Steinberg (2004). Handbook of Adolescent Psychology. John Wiley & Sons. pp. 193–196. ISBN 978-0471690443. Retrieved April 29, 2013. When researchers use the term sex, they nearly always mean sexual intercourse – more specifically, penile–vaginal intercourse. [...] The widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.'
   • Fedwa Malti-Douglas (2007). Encyclopedia of Sex and Gender: A-C. Macmillan Reference. p. 308. ISBN 978-0028659619. Sexual intercourse. [T]he term coitus indicates a specific act of sexual intercourse that also is known as coition or copulation. This 'coming together' is generally understood in heteronormative terms as the penetration of a woman's vagina by a man's penis.
   • Irving B. Weiner; W. Edward Craighead (2010). The Corsini Encyclopedia of Psychology. 4. John Wiley & Sons. p. 1577. ISBN 978-0470170236. Retrieved August 21, 2013. Human sexual intercourse, or coitus, is one of the most common sexual outlets among adults. Sexual intercourse generally refers to penile penetration of the vagina.
   • Clint E. Bruess; Elizabeth Schroeder (2013). Sexuality Education Theory and Practice. Jones & Bartlett Publishers. p. 152. ISBN 978-1449649289. Retrieved December 5, 2014. In many cultures around the world, vaginal sex is what is usually implied when people refer to 'having sex' or 'sexual intercourse.' It is the most frequently studied behavior and is often the focus of sexuality education programming for youth.
   • Cecie Starr; Beverly McMillan (2015). Human Biology. Cengage Learning. p. 339. ISBN 978-1305445949. Retrieved December 27, 2017. Coitus and copulation are both technical terms for sexual intercourse. The male sex act involves an erection, in which the limp penis stiffens and lengthens. It also involves ejaculation, the forceful expulsion of semen into the urethra and out from the penis. [...] During coitus, pelvic thrusts stimulate the penis as well as the female's clitoris and vaginal wall. The stimulation triggers rhythmic, involuntary contractions in smooth muscle in the male reproductive tract, especially the vas deferens and the prostate. The contractions rapidly force sperm out of each epididymis. They also force the contents of seminal vesicles and the prostate gland into the urethra. The resulting mixture, semen, is ejaculated into the vagina.
   • Janell L. Carroll (2018). Sexuality Now: Embracing Diversity. Cengage Learning. p. 289. ISBN 978-1337672061. Retrieved November 22, 2019. Vaginal intercourse (also referred to as sexual intercourse) involves inserting the penis into the vagina.
2. Alters S (2012). Essential Concepts for Healthy Living. Jones & Bartlett Publishers. pp. 180–181. ISBN 978-1449630621. Most heterosexuals are familiar with the notion of 'having sex' or sexual intercourse as vaginal sex, the insertion of a penis into a vagina. Vaginal sex, or coitus, is the most common and popular form of intimate sexual activity between partners.
3. Carroll JL (2018). Sexuality Now: Embracing Diversity. Cengage Learning. p. 289. ISBN 978-1337672061. Vaginal intercourse (also referred to as sexual intercourse) involves inserting the penis into the vagina.
4. "Sexual Intercourse". Discovery.com. Archived from the original on August 22, 2008. Retrieved January 12, 2008.
5. Rathus SA, Nevid JS, Rathus LF (2010). Human Sexuality in a World of Diversity. Allyn & Bacon. p. 251. ISBN 978-0205786060.
6. Freberg L (2009). Discovering Biological Psychology. Cengage Learning. pp. 308–310. ISBN 978-0547177793.
7. "Defining sexual health: Report of a technical consultation on sexual health" (PDF). World Health Organization. January 2002. p. 4. Retrieved September 5, 2012. In English, the term 'sex' is often used to mean 'sexual activity' and can cover a range of behaviours. Other languages and cultures use different terms, with slightly different meanings.
8. • "Sexual Intercourse". Discovery.com. Archived from the original on August 22, 2008. Retrieved January 12, 2008.
   • Nancy W. Denney; David Quadagno (2008). Human Sexuality. Mosby-Year Book. p. 273. ISBN 978-0801663741. Although the term intercourse is usually used to refer to the insertion of the penis into the vagina, it is also used to refer to oral intercourse or anal intercourse in which the penis is inserted into the mouth or the anus, respectively.
9. • Ann O'Leary (2002). Beyond Condoms: Alternative Approaches to HIV Prevention. Springer. p. 155. ISBN 978-0306467318.
   • Dianne Hales (2015). An Invitation to Health: Live It Now! Brief Edition (3rd ed.). Cengage Learning. p. 251. ISBN 978-1305445956.
10. Kahn AP, Fawcett J (2008). The Encyclopedia of Mental Health. Infobase Publishing. p. 111. ISBN 978-0816064540.
11. Hales D (2008). An Invitation to Health Brief 2010–2011. Cengage Learning. pp. 269–271. ISBN 978-0495391920.
12. Kumar B, Gupta S (2014). Sexually Transmitted Infections. Elsevier Health Sciences. p. 93. ISBN 978-8131229781.
13. See page 11 onwards and pages 47–49 for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether a person has engaged in penile–vaginal sex. Carpenter LM (2005). Virginity Lost: An Intimate Portrait of First Sexual Experiences. NYU Press. pp. 295 pages. ISBN 978-0-8147-1652-6.
14. Strong B, DeVault C, Cohen TF (2010). The Marriage and Family Experience: Intimate Relationship in a Changing Society. Cengage Learning. p. 186. ISBN 978-0-534-62425-5. Retrieved October 8, 2011. Most people agree that we maintain virginity as long as we refrain from sexual (vaginal) intercourse. But occasionally we hear people speak of 'technical virginity' [...] Data indicate that 'a very significant proportion of teens ha[ve] had experience with oral sex, even if they haven't had sexual intercourse, and may think of themselves as virgins' [...] Other research, especially research looking into virginity loss, reports that 35% of virgins, defined as people who have never engaged in vaginal intercourse, have nonetheless engaged in one or more other forms of heterosexual sexual activity (e.g., oral sex, anal sex, or mutual masturbation).
15. Michael Kent (2000). Advanced biology. Oxford University Press. pp. 250–253. ISBN 978-0199141951. Retrieved October 21, 2015.
16. Showick Thorpe; Edgar Thorpe (2009). The Pearson General Studies Manual 2009, 1/e. Pearson Education India. p. 1.79. ISBN 978-8131721339. Retrieved October 21, 2015.
17. • Herbert L. Petri, John M. Govern (2012). Motivation: Theory, Research, and Application. Cengage Learning. p. 24. ISBN 978-1285401515.CS1 maint: uses authors parameter (link)
    • Bailey NW, Zuk M (August 2009). "Same-sex sexual behavior and evolution". Trends Ecol. Evol. 24 (8): 439–46. doi:10.1016/j.tree.2009.03.014. PMID 19539396.
18. Balcombe, Jonathan (2006). Pleasurable Kingdom: Animals and the Nature of Feeling Good. Palgrave Macmillan. pp. 106–118. ISBN 978-0230552272.
19. • "Coitus". Merriam-Webster.
    • Fedwa Malti-Douglas (2007). Encyclopedia of Sex and Gender: A-C. Macmillan Reference. p. 308. ISBN 978-0028659619. Sexual intercourse. [T]he term coitus indicates a specific act of sexual intercourse that also is known as coition or copulation. This 'coming together' is generally understood in heteronormative terms as the penetration of a woman's vagina by a man's penis.
    • Ada P. Kahn; Jan Fawcett (2008). The Encyclopedia of Mental Health. Infobase Publishing. p. 111. ISBN 978-0816064540.
20. See page 302 for orgasm information, and pages 285–286 for definitions, prevalence and length of sexual intercourse. Carroll JL (2012). Discovery Series: Human Sexuality (1st ed.). Cengage Learning. pp. 656 pages. ISBN 978-1111841898.
21. Milkman HB, Wanberg KW (2004). Pathways to Self-Discovery and Change: Criminal Conduct and Substance Abuse Treatment for Adolescents. SAGE. pp. 254–255. ISBN 978-1412906142.
22. Kinetics H (2009). Health and Wellness for Life. Human Kinetics. p. 207. ISBN 978-0736068505.
23. Barrows EM (2011). Animal Behavior Desk Reference: A Dictionary of Animal Behavior, Ecology, and Evolution. Taylor & Francis. pp. 122–124. ISBN 978-1439836514.
24. "Copulation". Dorland's Medical Dictionary for Health Consumers, 2007/TheFreeDictionary.com for various dictionary definitions. Retrieved September 6, 2012.
25. "Copulation". The American Heritage Dictionary of the English Language, Fifth Edition. 2011. Retrieved August 23, 2013.
26. • Ken Plummer (2002). Modern Homosexualities: Fragments of Lesbian and Gay Experiences. Routledge. pp. 187–191. ISBN 978-1134922420. Retrieved August 24, 2013. [S]ome sexual practices are regarded as inherently better (normal, natural, more satisfying) than others, with vaginal intercourse privileged as the 'Real Thing.' Such beliefs, influenced by views about sex as ultimately a reproductive function, continue to be perpetuated through discourses on sex despite a number of important contradictions.
    • Richard M. Lerner; Laurence Steinberg (2004). Handbook of Adolescent Psychology. John Wiley & Sons. pp. 193–196. ISBN 978-0471690443. When researchers use the term sex, they nearly always mean sexual intercourse – more specifically, penile–vaginal intercourse... The widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.'
    • See page 11 onwards and pages 47–49 for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether a person has engaged in penile–vaginal sex. Laura M. Carpenter (2005). Virginity Lost: An Intimate Portrait of First Sexual Experiences. NYU Press. pp. 295 pages. ISBN 978-0-8147-1652-6.
    • Fedwa Malti-Douglas (2007). Encyclopedia of Sex and Gender: A-C. Macmillan Reference. p. 308. ISBN 978-0028659619. Sexual intercourse. [T]he term coitus indicates a specific act of sexual intercourse that also is known as coition or copulation. This 'coming together' is generally understood in heteronormative terms as the penetration of a woman's vagina by a man's penis.
    • Irving B. Weiner; W. Edward Craighead (2010). The Corsini Encyclopedia of Psychology. 4. John Wiley & Sons. p. 1577. ISBN 978-0470170236. Retrieved August 21, 2013. Human sexual intercourse, or coitus, is one of the most common sexual outlets among adults. Sexual intercourse generally refers to penile penetration of the vagina.
    • Clint E. Bruess; Elizabeth Schroeder (2013). Sexuality Education Theory and Practice. Jones & Bartlett Publishers. p. 152. ISBN 978-1449649289. In many cultures around the world, vaginal sex is what is usually implied when people refer to 'having sex' or 'sexual intercourse'. It is the most frequently studied behavior and is often the focus of sexuality education programming for youth.
27. "Fuck". Merriam-Webster. Retrieved March 30, 2013.
28. "Shag". Merriam-Webster. Retrieved March 30, 2013.
29. "Sleep together". TheFreeDictionary.com. Retrieved March 30, 2013.
30. "Intromission". Merriam-Webster. Retrieved December 26, 2012.
31. "sexarche - oi". Concise Medical Dictionary. Oxford University Press. Retrieved July 4, 2017.
32. Lara LS, Abdo CH (2016). "Age at Time of Initial Sexual Intercourse and Health of Adolescent Girls". Journal of Pediatric and Adolescent Gynecology. 29 (5): 417–423. doi:10.1016/j.jpag.2015.11.012. ISSN 1083-3188. PMID 26655691.
33. • "Sexual Intercourse". Discovery.com. Archived from the original on August 22, 2008. Retrieved January 12, 2008.
    • Harvey B. Milkman; Kenneth W. Wanberg (2004). Pathways to Self-Discovery and Change: Criminal Conduct and Substance Abuse Treatment for Adolescents. SAGE. pp. 254–255. ISBN 978-1412906142.
    • Nancy W. Denney; David Quadagno (2008). Human Sexuality. Mosby-Year Book. p. 273. ISBN 978-0801663741.
34. • See page 11 onwards and pages 47–49 for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether a person has engaged in penile–vaginal sex. Laura M. Carpenter (2005). Virginity Lost: An Intimate Portrait of First Sexual Experiences. NYU Press. pp. 295 pages. ISBN 978-0-8147-1652-6. Retrieved October 9, 2011.
    • Bryan Strong; Christine DeVault; Theodore F. Cohen (2010). The Marriage and Family Experience: Intimate Relationship in a Changing Society. Cengage Learning. p. 186. ISBN 978-0-534-62425-5. Most people agree that we maintain virginity as long as we refrain from sexual (vaginal) intercourse. ...But occasionally we hear people speak of 'technical virginity' ... Other research, especially research looking into virginity loss, reports that 35% of virgins, defined as people who have never engaged in vaginal intercourse, have nonetheless engaged in one or more other forms of heterosexual activity (e.g. oral sex, anal sex, or mutual masturbation). ... Data indicate that 'a very significant proportion of teens ha[ve] had experience with oral sex, even if they haven't had sexual intercourse, and may think of themselves as virgins'.
    • Robert Crooks; Karla Baur (2010). Our Sexuality. Cengage Learning. pp. 286–289. ISBN 978-0495812944. Noncoital forms of sexual intimacy, which have been called outercourse, can be a viable form of birth control. Outercourse includes all avenues of sexual intimacy other than penile–vaginal intercourse, including kissing, touching, mutual masturbation, and oral and anal sex.
    • UD, TK (2014). Promoting Healthy Behaviour: A Practical Guide. Routledge. pp. 243–248. ISBN 978-1317818878.
35. • See page 11 onwards and pages 47–49 for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether a person has engaged in penile–vaginal sex. Laura M. Carpenter (2005). Virginity Lost: An Intimate Portrait of First Sexual Experiences. NYU Press. pp. 295 pages. ISBN 978-0-8147-1652-6. Retrieved October 9, 2011.
    • Bryan Strong; Christine DeVault; Theodore F. Cohen (2010). The Marriage and Family Experience: Intimate Relationship in a Changing Society. Cengage Learning. p. 186. ISBN 978-0-534-62425-5. Most people agree that we maintain virginity as long as we refrain from sexual (vaginal) intercourse. ...But occasionally we hear people speak of 'technical virginity' ... Other research, especially research looking into virginity loss, reports that 35% of virgins, defined as people who have never engaged in vaginal intercourse, have nonetheless engaged in one or more other forms of heterosexual activity (e.g. oral sex, anal sex, or mutual masturbation). ... Data indicate that 'a very significant proportion of teens ha[ve] had experience with oral sex, even if they haven't had sexual intercourse, and may think of themselves as virgins'.
    • UD, TK (2014). Promoting Healthy Behaviour: A Practical Guide. Routledge. pp. 243–248. ISBN 978-1317818878.
36. Gross MJ (2003). Like a Virgin. The Advocate. Here Publishing. pp. 44–45. 0001-8996. Retrieved March 13, 2011.
37. Dolby T (February 2004). "Why Some Gay Men Don't Go All The Way". Out. pp. 76–77. Retrieved February 12, 2011.
38. Lerner RM, Steinberg L (2004). Handbook of Adolescent Psychology. John Wiley & Sons. pp. 193–196. ISBN 978-0471690443. When researchers use the term sex, they nearly always mean sexual intercourse – more specifically, penile–vaginal intercourse... The widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.'
39. Greenberg JS, Bruess CE, Conklin SC (2007). Exploring the Dimensions of Human Sexuality. Jones & Bartlett Learning. p. 429. ISBN 978-0-7637-4148-8. 9780763741488.
40. Weiten W, Dunn DS, Hammer EY (2016). Psychology Applied to Modern Life: Adjustment in the 21st Century. Cengage Learning. p. 349. ISBN 978-0-7637-4148-8. 1305968476. Retrieved December 27, 2017.
41. • Richard D. McAnulty; M. Michele Burnette (2003). Exploring Human Sexuality: Making Healthy Decisions. Allyn & Bacon. p. 229. ISBN 978-0205380596. 9780763741488.
    • Richard M. Lerner; Laurence Steinberg (2004). Handbook of Adolescent Psychology. John Wiley & Sons. pp. 193–196. ISBN 978-0471690443. When researchers use the term sex, they nearly always mean sexual intercourse – more specifically, penile–vaginal intercourse... The widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.'
    • See page 11 onwards and pages 47–49 for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether a person has engaged in penile–vaginal sex. Laura M. Carpenter (2005). Virginity Lost: An Intimate Portrait of First Sexual Experiences. NYU Press. pp. 295 pages. ISBN 978-0-8147-1652-6. Retrieved October 9, 2011.
    • Andrew Baum; Tracey A. A. Revenson; Jerome Singer (2012). Handbook of Health Psychology (2nd ed.). Psychology Press. pp. 259–260. ISBN 978-0805864618.
    • Aggleton P, Ball A, Mane P (2013). Sex, Drugs and Young People: International Perspectives. Routledge. p. 74. ISBN 978-1134333103. Having started with a discussion of penile-vaginal intercourse as the act that designates sexual initiation, as defined in most studies, we would like to undercut that position by stressing the need to define sex more broadly.
42. McClelland SI (2012). "Measuring Sexual Quality of Life: Ten Recommendations for Health Psychologists". In Baum A, Revenson TA, Singer J (eds.). Handbook of Health Psychology (2nd ed.). Psychology Press. pp. 259–260. ISBN 978-0805864618. Retrieved April 30, 2013.
43. Kalbfleisch PJ, Cody MJ (2012). Gender Power and Communication in Human Relationships. Routledge. p. 153. ISBN 978-1136480508. Retrieved April 30, 2013.
44. UD, TK (2014). Promoting Healthy Behaviour: A Practical Guide. Routledge. pp. 243–248. ISBN 978-1317818878.
45. Aggleton P, Ball A, Mane P (2013). Sex, Drugs and Young People: International Perspectives. Routledge. pp. 74–75. ISBN 978-1134333103.
46. "Oral Sex and HIV Risk" (PDF). Centers for Disease Control and Prevention (CDC). June 2009. Archived from the original (PDF) on May 10, 2013. Retrieved August 30, 2013.
47. Jonathan Engel (2009). The Epidemic: A History of Aids. HarperCollins. p. 242. ISBN 978-0061856761. Retrieved August 30, 2013. Many men simply did not like the feel of condoms, or associated them with emasculation. They say, 'Unless it's flesh on flesh, it's not real sex...
48. Naomi N. Wekwete (2010). Adolescent Pregnancy Challenges in the Era of HIV and AIDS: A Case Study of a Selected Rural Area in Zimbabwe. African Books Collective. p. 49. ISBN 978-9994455485. Retrieved August 30, 2013.
49. Wayne Weiten; Margaret A. Lloyd; Dana S. Dunn; Elizabeth Yost Hammer (2008). Psychology Applied to Modern Life: Adjustment in the 21st Century. Cengage Learning. pp. 422–423. ISBN 978-0495553397. Retrieved January 5, 2012. The man-above, or "missionary," position is the most common [sex position].
50. Taormino, Tristan (2009). The Big Book of Sex Toys. Quiver. p. 52. ISBN 978-1-59233-355-4. Retrieved June 9, 2014.
51. Wayne Weiten; Dana S. Dunn; Elizabeth Yost Hammer (2011). Psychology Applied to Modern Life: Adjustment in the 21st Century. Cengage Learning. pp. 384–386. ISBN 978-1-111-18663-0. Retrieved January 5, 2012.
52. Sandra Alters; Wendy Schiff (2011). Essential Concepts for Healthy Living Update. Jones & Bartlett Publishers. p. 154. ISBN 978-1449653743. Retrieved December 9, 2014.
53. Pfaus J.G., Flanagan-Cato L.M., Blaustein J.D. (2015) Female sexual behavior. in Plant T., Zeleznik A. (Eds). Knobil and Neill's Physiology of Reproduction. Academic Press, 4th edition
54. Harry T. Reis; Susan Sprecher; Susan K. Sprecher (2009). Encyclopedia of Human Relationships. 1. SAGE. pp. 541–543. ISBN 978-1412958462.
55. Dixson A.F. (2012) Primate sexuality: Comparative studies of the Prosimians, Monkeys, Apes, and Human Beings. Oxford University Press, 2nd edition.
56. Doty R.L. (2014) Human Pheromones: Do They Exist? in Mucignat-Caretta C. (Ed). Neurobiology of Chemical Communication. Boca Raton (FL): CRC Press, (19).
57. Keath Roberts (2006). Sex. Lotus Press. p. 145. ISBN 978-8189093594. Retrieved August 17, 2012.
58. Cecie Starr; Beverly McMillan (2008). Human Biology. Cengage Learning. p. 314. ISBN 978-0495561811. Retrieved April 30, 2013.
59. Joseph A. Flaherty; John Marcell Davis; Philip G. Janicak (1993). Psychiatry: Diagnosis & therapy. A Lange clinical manual. Appleton & Lange (Original from Northwestern University). pp. 544 pages. ISBN 978-0-8385-1267-8. The amount of time of sexual arousal needed to reach orgasm is variable — and usually much longer — in women than in men; thus, only 20–30% of women attain a coital climax. b. Many women (70–80%) require manual clitoral stimulation...
60. Mah K, Binik YM (January 7, 2001). "The nature of human orgasm: a critical review of major trends". Clinical Psychology Review. 21 (6): 823–856. doi:10.1016/S0272-7358(00)00069-6. PMID 11497209. Women rated clitoral stimulation as at least somewhat more important than vaginal stimulation in achieving orgasm; only about 20% indicated that they did not require additional clitoral stimulation during intercourse.
61. Kammerer-Doak D, Rogers RG (June 2008). "Female Sexual Function and Dysfunction". Obstetrics and Gynecology Clinics of North America. 35 (2): 169–183. doi:10.1016/j.ogc.2008.03.006. PMID 18486835. Most women report the inability to achieve orgasm with vaginal intercourse and require direct clitoral stimulation ... About 20% have coital climaxes...
62. Elisabeth Anne Lloyd (2005). The case of the female orgasm: bias in the science of evolution. Harvard University Press. p. 53. ISBN 978-0-674-01706-1. Retrieved January 5, 2012.
63. O'Connell HE, Sanjeevan KV, Hutson JM (October 2005). "Anatomy of the clitoris". The Journal of Urology. 174 (4 Pt 1): 1189–95. doi:10.1097/01.ju.0000173639.38898.cd. PMID 16145367. S2CID 26109805. Lay summary – BBC News (June 11, 2006).
64. Hurlbert DF, Apt C (1995). "The coital alignment technique and directed masturbation: a comparative study on female orgasm". Journal of Sex & Marital Therapy. 21 (1): 21–29. doi:10.1080/00926239508405968. PMID 7608994.
65. Barry R. Komisaruk; Beverly Whipple; Sara Nasserzadeh; Carlos Beyer-Flores (2009). The Orgasm Answer Guide. JHU Press. pp. 108–109. ISBN 978-0-8018-9396-4. Retrieved November 6, 2011.
66. Paula Kamen (2000). Her Way: Young Women Remake the Sexual Revolution. New York University Press. pp. 74–77. ISBN 978-0814747339. Retrieved September 5, 2012.
67. Hite, Shere (2003). The Hite Report: A Nationwide Study of Female Sexuality. New York, NY: Seven Stories Press. pp. 512 pages. ISBN 978-1-58322-569-1. Retrieved March 2, 2012.
68. Carroll, Janell L. (2009). Sexuality Now: Embracing Diversity. Cengage Learning. pp. 118, 252, and 264. ISBN 978-0-495-60274-3. Retrieved June 23, 2012.
69. Dunson, D.B.; Baird, D.D.; Wilcox, A.J.; Weinberg, C.R. (1999). "Day-specific probabilities of clinical pregnancy based on two studies with imperfect measures of ovulation". Human Reproduction. 14 (7): 1835–1839. doi:10.1093/humrep/14.7.1835. ISSN 1460-2350. PMID 10402400.
70. Richard Evan Jones; Kristin H. López (2006). Human Reproductive Biology. Academic Press. pp. 604 pages. ISBN 978-0120884650. Retrieved November 8, 2012.
71. Cecie Starr; Beverly McMillan (2015). Human Biology. Cengage Learning. p. 339. ISBN 978-1305445949. Retrieved December 27, 2017.
72. Pages.242,374 in: Weschler, Toni (2002). Taking Charge of Your Fertility (Revised ed.). New York: HarperCollins. pp. 359–361. ISBN 978-0-06-093764-5.
73. "How to get pregnant". Mayo Clinic. November 2, 2016. Retrieved February 16, 2018.
74. "Fertility problems: assessment and treatment, Clinical guideline [CG156]". National Institute for Health and Care Excellence. Retrieved February 16, 2018. Published date: February 2013. Last updated: September 2017
75. Dr. Philip B. Imler & David Wilbanks (November 2019). "The Essential Guide to Getting Pregnant" (PDF). American Pregnancy Association.
76. James Bobick; Naomi Balaban (2008). The Handy Anatomy Answer Book. Visible Ink Press. pp. 306–307. ISBN 978-1578593286. Retrieved August 21, 2013.
77. R.K. Sharma (2007). Concise Textbook Of Forensic Medicine & Toxicology. Elsevier India. pp. 113–116. ISBN 978-8131211458. Retrieved October 13, 2013.
78. Mosby, Marie T. O'Toole (2013). Mosby's Medical Dictionary. Elsevier Health Sciences. p. 138. ISBN 978-0323112581. Retrieved October 13, 2013.
79. Berkowitz D, Marsiglio W (2007). "Gay Men: Negotiating Procreative, Father, and Family Identities". Journal of Marriage and Family. 69 (2): 366–381. doi:10.1111/j.1741-3737.2007.00371.x. S2CID 38458107.
80. Joan M. Burda (2008). Gay, lesbian, and transgender clients: a lawyer's guide. American Bar Association. pp. 69–74. ISBN 978-1-59031-944-4. Retrieved July 28, 2011.
81. Jerry D. Durham; Felissa R. Lashley (2000). The Person With HIV/AIDS: Nursing Perspectives (3rd ed.). Springer Publishing Company. p. 103. ISBN 978-8122300048. Retrieved January 29, 2012.
82. Robert Crooks; Karla Baur (2010). Our Sexuality. Cengage Learning. pp. 286–289. ISBN 978-0495812944. Retrieved August 30, 2012. Noncoital forms of sexual intimacy, which have been called outercourse, can be a viable form of birth control. Outercourse includes all avenues of sexual intimacy other than penile–vaginal intercourse, including kissing, touching, mutual masturbation, and oral and anal sex.
83. Feldmann J, Middleman AB (2002). "Adolescent sexuality and sexual behavior". Current Opinion in Obstetrics and Gynecology. 14 (5): 489–493. doi:10.1097/00001703-200210000-00008. PMID 12401976.
84. Thomas, R. Murray (2009). Sex and the American teenager seeing through the myths and confronting the issues. Lanham, Md.: Rowman & Littlefield Education. p. 81. ISBN 9781607090182. Retrieved October 21, 2015.
85. Edlin, Gordon (2012). Health & Wellness. Jones & Bartlett Learning. p. 213. ISBN 9781449636470. Retrieved October 21, 2015.
86. Chin HB, Sipe TA, Elder R, Mercer SL, Chattopadhyay SK, Jacob V, Wethington HR, Kirby D, Elliston DB, Griffith M, Chuke SO, Briss SC, Ericksen I, Galbraith JS, Herbst JH, Johnson RL, Kraft JM, Noar SM, Romero LM, Santelli J (2012). "The Effectiveness of Group-Based Comprehensive Risk-Reduction and Abstinence Education Interventions to Prevent or Reduce the Risk of Adolescent Pregnancy, Human Immunodeficiency Virus, and Sexually Transmitted Infections". American Journal of Preventive Medicine. 42 (3): 272–294. doi:10.1016/j.amepre.2011.11.006. PMID 22341164.
87. National Institute of Allergy and Infectious Diseases; National Institutes of Health, Department of Health and Human Services (July 20, 2001). Workshop Summary: Scientific Evidence on Condom Effectiveness for Sexually Transmitted Disease (STD) Prevention (PDF). Hyatt Dulles Airport, Herndon, Virginia. pp. 13–15. Archived from the original (PDF) on March 7, 2010. Retrieved March 20, 2009.
88. "Effectiveness of male latex condoms in protecting against pregnancy and sexually transmitted infections". World Health Organization. 2000. Archived from the original on May 9, 2010. Retrieved July 23, 2013.
89. Bhushan Kumar, Somesh Gupta (2014). Sexually Transmitted Infections E book. Elsevier Health Sciences. p. 122. ISBN 978-8131229781.
90. Dianne Hales (2010). An Invitation to Health: Choosing to Change. Cengage Learning. pp. 301–302. ISBN 978-0538736558. Retrieved March 30, 2013.
91. Winner B, Peipert JF, Zhao Q, Buckel C, Madden T, Allsworth JE, Secura GM (2012). "Effectiveness of long-acting reversible contraception". N. Engl. J. Med. 366 (21): 1998–2007. doi:10.1056/NEJMoa1110855. PMID 22621627.
92. "Findings from the National Survey of Sexual Health and Behavior, Centre for Sexual Health Promotion, Indiana University". The Journal of Sexual Medicine. 7, Supplement 5.: 4 2010. Retrieved March 4, 2011.
93. Clint E. Bruess; Elizabeth Schroeder (2013). Sexuality Education Theory and Practice. Jones & Bartlett Publishers. p. 152. ISBN 978-1449649289. Retrieved December 5, 2014.
94. Bozon, Michael (2003). "At what age do women and men have their first sexual intercourse? World comparisons and recent trends" (PDF). Population and Societies. 391: 1–4. Archived from the original (PDF) on March 4, 2016.
95. Graziella Caselli; Guillaume Wunsch; Daniel Courgeau; Jacques Vallin (2005). Demography – Analysis and Synthesis: A Treatise in Population. Academic Press. pp. 490–501. ISBN 978-0127656601. Retrieved September 6, 2013.
96. "Key Statistics from the National Survey of Family Growth". Centers for Disease Control and Prevention (CDC). Retrieved February 9, 2013.
97. "Teenagers in the United States: Sexual Activity, Contraceptive Use, and Childbearing, 2006–2010 National Survey of Family Growth" (PDF). Centers for Disease Control and Prevention (CDC). Retrieved December 26, 2012.
98. "Teenagers in the United States: Sexual Activity, Contraceptive Use, and Childbearing, 2002" (PDF). Centers for Disease Control and Prevention (CDC). Retrieved February 9, 2013.
99. Andrew Steptoe; Kenneth Freedland; J. Richard Jennings; Maria M. Llabre; Stephen B Manuck; Elizabeth J. Susman (2010). Handbook of Behavioral Medicine: Methods and Applications. Springer Science & Business Media. pp. 60–61. ISBN 978-0387094885. Retrieved December 7, 2014.
100. Theresa Hornstein; Jeri Schwerin (2012). Biology of Women. Cengage Learning. p. 205. ISBN 978-1285401027. Retrieved December 7, 2014.
101. Carol Sigelman; Elizabeth Rider (2011). Life-Span Human Development. Cengage Learning. p. 452. ISBN 978-1111342739. Retrieved December 7, 2014.
102. Northrup, Christiane (2010). Women's Bodies, Women's Wisdom: Creating Physical and Emotional Health and Healing. Bantam. p. 232. ISBN 978-0-553-80793-6. Retrieved October 21, 2015.
103. Hoeger W, HS, FA, HC (2016). Principles and Labs for Fitness and Wellness. Cengage Learning. pp. 538–540. ISBN 978-1337099974.
104. "Sexually transmitted infections". womenshealth.gov. February 22, 2017. Retrieved December 8, 2017. This article incorporates text from this source, which is in the public domain.
105. GM, MJ (2016). Nursing Care Plans - E-Book: Diagnoses, Interventions, and Outcomes. Elsevier Health Sciences. p. 725. ISBN 978-0323428101.
106. Murray PR, Rosenthal KS, Pfaller MA (2013). Medical microbiology (7th ed.). St. Louis, MO: Mosby. p. 418. ISBN 978-0-323-08692-9. Archived from the original on December 1, 2015.
107. Goering, Richard V. (2012). Mims' medical microbiology (5th ed.). Edinburgh: Saunders. p. 245. ISBN 978-0-7234-3601-0.
108. "STD Trends in the United States: 2010 National Data for Gonorrhea, Chlamydia, and Syphilis". Centers for Disease Control and Prevention. Retrieved September 15, 2012.
109. "Sexually transmitted infections (STIs)". World Health Organization. Retrieved June 20, 2015.
110. CDC Hepatitis B Information for Health Professionals Accessed May 27, 2010
111. "Hepatitis B". World Health Organization. July 18, 2018.
112. "HIV/AIDS". World Health Organization. Retrieved September 15, 2012.
113. "HIV/AIDS". Fact sheet N° 360. World Health Organization. July 2012. Retrieved September 8, 2012.
114. "Not Every Pregnancy is Welcome". The world health report 2005 – make every mother and child count. World Health Organization. Retrieved December 6, 2011.
115. "Get "In the Know": 20 Questions About Pregnancy, Contraception and Abortion". Guttmacher Institute. 2005. Archived from the original on December 23, 2009. Retrieved March 4, 2011.CS1 maint: unfit url (link)
116. Ventura, SJ; Abma, JC; Mosher, WD & Henshaw, S. (November 16, 2007). "Estimated pregnancy rates for the United States, 1990–2000: An Update. National Vital Statistics Reports, 52 (23)" (PDF). Centers for Disease Control and Prevention. Retrieved March 4, 2011.
117. Blum K, Werner T, Carnes S, Carnes P, Bowirrat A, Giordano J, Oscar-Berman M, Gold M (2012). "Sex, drugs, and rock 'n' roll: hypothesizing common mesolimbic activation as a function of reward gene polymorphisms". Journal of Psychoactive Drugs. 44 (1): 38–55. doi:10.1080/02791072.2012.662112. PMC 4040958. PMID 22641964.
118. Olsen CM (December 2011). "Natural rewards, neuroplasticity, and non-drug addictions". Neuropharmacology. 61 (7): 1109–1122. doi:10.1016/j.neuropharm.2011.03.010. PMC 3139704. PMID 21459101.
119. Pitchers KK, Vialou V, Nestler EJ, Laviolette SR, Lehman MN, Coolen LM (February 2013). "Natural and drug rewards act on common neural plasticity mechanisms with ΔFosB as a key mediator". J. Neurosci. 33 (8): 3434–42. doi:10.1523/JNEUROSCI.4881-12.2013. PMC 3865508. PMID 23426671.
120. Probst, Catharina C.; van Eimeren, Thilo (2013). "The Functional Anatomy of Impulse Control Disorders". Current Neurology and Neuroscience Reports. 13 (10): 386. doi:10.1007/s11910-013-0386-8. ISSN 1528-4042. PMC 3779310. PMID 23963609.
121. Guilleminault, Christian; Miglis, Mitchell (2014). "Kleine-Levin syndrome: a review". Nature and Science of Sleep. 6: 19–26. doi:10.2147/NSS.S44750. ISSN 1179-1608. PMC 3901778. PMID 24470783.
122. Nicolas Kipshidze; Jawad Fareed; Patrick W. Serruys; Jeff Moses (2007). Textbook of Interventional Cardiovascular Pharmacology. CRC Press. p. 505. ISBN 978-0203463048. Retrieved October 21, 2015.
123. Dahabreh, Issa J. (March 23, 2011). "Association of Episodic Physical and Sexual Activity With Triggering of Acute Cardiac Events. Systematic Review and Meta-analysis". JAMA: The Journal of the American Medical Association. 305 (12): 1225–33. doi:10.1001/jama.2011.336. PMC 5479331. PMID 21427375. Acute cardiac events were significantly associated with episodic physical and sexual activity; this association was attenuated among persons with high levels of habitual physical activity.
124. John Wincze (2009). Enhancing Sexuality : A Problem-Solving Approach to Treating Dysfunction. Oxford University Press. pp. 56–60. ISBN 978-0199718023.
125. Hartmut Porst; Jacques Buvat (2008). Standard Practice in Sexual Medicine. John Wiley & Sons. p. 189. ISBN 978-1405178723. Retrieved October 22, 2013.
126. Emmanuele A. Jannini; Chris G. McMahon; Marcel D. Waldinger (2012). Premature Ejaculation: From Etiology to Diagnosis and Treatment. Springer. pp. 159–162. ISBN 978-8847026469. Retrieved October 22, 2013.
127. June M. Reinisch; Ruth Beasley (1991). The Kinsey Institute New Report On Sex. Macmillan. pp. 129–130. ISBN 978-0312063863. Retrieved August 30, 2012.
128. Corty EW, Guardiani JM (2008). "Canadian and American Sex Therapists' Perceptions of Normal and Abnormal Ejaculatory Latencies: How Long Should Intercourse Last?". The Journal of Sexual Medicine. 5 (5): 1251–1256. doi:10.1111/j.1743-6109.2008.00797.x. PMID 18331255.
129. Vern L Bullough; Bonnie Bullough (2014). Human Sexuality: An Encyclopedia. Routledge. p. 32. ISBN 978-1135825027. Retrieved December 6, 2014.
130. Rosenthal, Martha (2012). Human Sexuality: From Cells to Society. Cengage Learning. p. 150. ISBN 9780618755714. Retrieved October 22, 2013.
131. Irving B. Weiner; George Stricker; Thomas A. Widiger (2012). Handbook of Psychology, Clinical Psychology. John Wiley & Sons. pp. 172–175. ISBN 978-1118404430. Retrieved October 22, 2013.
132. Rod Plotnik; Haig Kouyoumdjian (2010). Introduction to Psychology. Cengage Learning. p. 344. ISBN 978-0495903444. Inhibited female orgasm refers to a persistent delay or absence of orgasm after becoming aroused and excited. About 10% of women never reach orgasm...
133. Knoepp LR, Shippey SH, Chen CC, Cundiff GW, Derogatis LR, Handa VL (2010). "Sexual complaints, pelvic floor symptoms, and sexual distress in women over forty". The Journal of Sexual Medicine. 7 (11): 3675–82. doi:10.1111/j.1743-6109.2010.01955.x. PMC 3163299. PMID 20704643.
134. Fred F. Ferri (2012). Ferri's Clinical Advisor 2013,5 Books in 1, Expert Consult — Online and Print,1: Ferri's Clinical Advisor 2013. Elsevier Health Sciences. p. 1134. ISBN 978-0323083737. Retrieved November 29, 2014.
135. Marlene B. Goldman; Rebecca Troisi; Kathryn M. Rexrode (2012). Women and Health. Academic Press. p. 351. ISBN 978-0123849793. Retrieved December 6, 2014.
136. Ronald J. Comer (2010). Fundamentals of Abnormal Psychology. Macmillan. p. 338. ISBN 978-1429216333. Retrieved December 6, 2014.
137. Schouten BW, Bohnen AM, Groeneveld FP, Dohle GR, Thomas S, Bosch JL (July 2010). "Erectile dysfunction in the community: trends over time in incidence, prevalence, GP consultation and medication use—the Krimpen study: trends in ED". J Sex Med. 7 (7): 2547–53. doi:10.1111/j.1743-6109.2010.01849.x. PMID 20497307.
138. "Premature ejaculation". Mayo Clinic.com. Retrieved March 2, 2007.
139. "Guideline on the pharmacologic management of premature ejaculation" (PDF). American Urological Association. 2004. Archived from the original (PDF) on March 3, 2016. Retrieved October 12, 2013.
140. Jerrold S Greenberg; Clint E. Bruess; Dean Emeritus (2010). Exploring the Dimensions of Human Sexuality. Jones & Bartlett Publishers. p. 633. ISBN 978-0763797409. Retrieved December 8, 2014.
141. Richard Balon; Robert Taylor Segraves (2009). Clinical Manual of Sexual Disorders. American Psychiatric Pub. p. 292. ISBN 978-1585629053. Retrieved December 6, 2014.
142. The Architects' Journal. 221. Architectural Press. 2005. p. 16. Retrieved December 6, 2014.
143. Richard Balon; Robert Taylor Segraves (2009). Clinical Manual of Sexual Disorders. American Psychiatric Pub. p. 281. ISBN 978-1585629053. Retrieved December 6, 2014.
144. Hoffman, Barbara (2012). Williams gynecology (2nd ed.). New York: McGraw-Hill Medical. p. 65. ISBN 978-0071716727.
145. Tristano, Antonio G (2014). "Impact of rheumatoid arthritis on sexual function". World Journal of Orthopedics. 5 (2): 107–11. doi:10.5312/wjo.v5.i2.107. ISSN 2218-5836. PMC 4017303. PMID 24829873.
146. Deyo, R. A.; Von Korff, M.; Duhrkoop, D. (2015). "Opioids for low back pain". BMJ. 350 (jan05 10): g6380. doi:10.1136/bmj.g6380. ISSN 1756-1833. PMC 6882374. PMID 25561513.
147. Herson, Paco S.; Palmateer, Julie; Hurn, Patricia D. (2012). "Biological Sex and Mechanisms of Ischemic Brain Injury". Translational Stroke Research. 4 (4): 413–419. doi:10.1007/s12975-012-0238-x. ISSN 1868-4483. PMC 3733393. PMID 23930140.
148. Donna Falvo (2013). Medical and Psychosocial Aspects of Chronic Illness and Disability. Jones & Bartlett Publishers. p. 367. ISBN 978-1449694425. Retrieved December 7, 2014.
149. Alcohol Use and Sexual Risk Behaviour: A Cross-cultural Study in Eight Countries. World Health Organization. 2005. pp. 135 pages. ISBN 978-9241562898. Retrieved March 30, 2013.
150. Peter Aggleton; Andrew Ball; Purnima Mane (2013). Sex, Drugs and Young People: International Perspectives. Routledge. pp. 130–133. ISBN 978-1134333097. Retrieved December 7, 2014.
151. Greenwood, Nechama W.; Wilkinson, Joanne (2013). "Sexual and Reproductive Health Care for Women with Intellectual Disabilities: A Primary Care Perspective". International Journal of Family Medicine. 2013: 1–8. doi:10.1155/2013/642472. ISSN 2090-2042. PMC 3876698. PMID 24455249.
152. HJ, WA, SS (2004). The Handbook of Sexuality in Close Relationships. Psychology Press. pp. 172–173. ISBN 1135624704.
153. Victor C. De Munck (1998). Romantic Love and Sexual Behavior: Perspectives from the Social Sciences. Greenwood Publishing Group. pp. 148–149. ISBN 978-0275957261. Retrieved December 9, 2014.
154. Tasha R. Howe (2011). Marriages and Families in the 21st Century: A Bioecological Approach. John Wiley & Sons. p. 411. ISBN 978-1405195010. Retrieved December 9, 2014.
155. Mark A Fine; John H. Harvey (2013). Handbook of Divorce and Relationship Dissolution. Psychology Press. p. 160. ISBN 978-1317824213. Retrieved December 9, 2014.
156. June M. Reinisch; Ruth Beasley (1991). The Kinsey Institute New Report On Sex. Macmillan. p. 74. ISBN 978-0312063863. Retrieved December 9, 2014.
157. Pepper Schwartz; Virginia Rutter (1998). The Gender of Sexuality. Rowman & Littlefield. p. 129. ISBN 978-0803990425. Retrieved December 9, 2014.
158. William Yarber; Barbara Sayad; Bryan Strong (2012). Human Sexuality: Diversity in Contemporary America (Eighth ed.). McGraw-Hill Higher Education. p. 445. ISBN 978-0077435257. Retrieved December 9, 2014.
159. Beth Montemurro (2014). Deserving Desire: Women's Stories of Sexual Evolution. Rutgers University Press. p. 169. ISBN 978-0813573069. Retrieved December 9, 2014.
160. Michael Gurian (2013). The Wonder of Aging: A New Approach to Embracing Life After Fifty. Simon & Schuster. p. 178. ISBN 978-1476706719. Retrieved December 9, 2014.
161. Bryan Strong; Theodore Cohen (2013). The Marriage and Family Experience: Intimate Relationships in a Changing Society. Cengage Learning. p. 212. ISBN 978-1285531892. Retrieved December 9, 2014.
162. Ponton, Lynn (2000). The Sex Lives of Teenagers. Dutton Publishing. p. 3. ISBN 978-0-452-28260-5.
163. Ralph J. DiClemente; John S. Santelli; Richard A. Crosby (2009). Adolescent Health: Understanding and Preventing Risk Behaviors. John Wiley & Sons. pp. 521–522. ISBN 978-0470452790. Retrieved December 7, 2014.
164. Jamie L Abaied; Deepika Anand; Tracey L Auster; Daniel BE (2014). The Oxford Handbook of Depression and Comorbidity. Oxford University Press. p. 450. ISBN 978-0199797004. Retrieved December 7, 2014.
165. Kevin Ryan; James Cooper (2008). Those Who Can, Teach. Cengage Learning. p. 110. ISBN 978-0547204888. Retrieved December 9, 2014.
166. Lerner RM, Perkins DF (1999). Social Interactions in Adolescence and Promoting Positive Social Contributions of Youth. Taylor & Francis. p. 124. ISBN 978-0815332954. Retrieved April 14, 2017.
167. Kowalski RM, Leary MR (2004). The Interface of Social and Clinical Psychology: Key Readings. Psychology Press. p. 121. ISBN 978-1841690872. Retrieved April 14, 2017.
168. Mary H. Guindon (2009). Self-Esteem Across the Lifespan: Issues and Interventions. Taylor & Francis. p. 147. ISBN 978-1841690872. Retrieved April 14, 2017.
169. Lisa Arai (2009). Teenage Pregnancy: The Making and Unmaking of a Problem. Policy Press. p. 147. ISBN 978-1847420749. Retrieved April 14, 2017.
170. Madsen S., Collins W. A. (2005). Differential predictions of young adult romantic relationships from transitory vs. longer romantic experiences during adolescence. Presented at Biennial Meeting of the Society for Research on Child Development, Atlanta, Georgia.
171. Seiffge-Krenke I., Lang J. (2002). Forming and maintaining romantic relations from early adolescence to young adulthood: evidence of a developmental sequence. Presented at 19th Biennial Meeting of the Society for Research on Adolescence, New Orleans, Louisiana.
172. Pearce MJ, Boergers J, Prinstein MJ (2002). "Adolescent obesity, overt and relational peer victimization, and romantic relationships". Obesity Research. 10 (5): 386–93. doi:10.1038/oby.2002.53. PMID 12006638. S2CID 154577.
173. Zimmer-Gembeck MJ, Siebenbruner J, Collins WA (2004). "A prospective study of intraindividual and peer influences on adolescents' heterosexual romantic and sexual behavior". Archives of Sexual Behavior. 33 (4): 381–394. doi:10.1023/B:ASEB.0000028891.16654.2c. PMID 15162084.
174. William N. Eskridge Jr. Dishonorable Passions: Sodomy Laws in America, 1861–2003. (2008) Viking Adult. ISBN 0-670-01862-7
175. Noelle N. R. Quenivet. Sexual Offenses in Armed Conflict & International Law. (2005) Hotei Publishing. ISBN 1-57105-341-7
176. Marshall Cavendish Corporation (2010). Sex and Society. Marshall Cavendish Corporation. pp. 143–144. ISBN 978-0-7614-7906-2. Retrieved August 25, 2013.
177. Jerrold S. Greenberg; Clint E. Bruess; Sarah C. Conklin (2010). Exploring the Dimensions of Human Sexuality. Jones & Bartlett Learning. p. 515. ISBN 978-0-7637-7660-2. Retrieved August 25, 2013.
178. Karen L. Kinnear (2007). Childhood Sexual Abuse: A Reference Handbook. ABC-CLIO. p. 89. ISBN 978-1-85109-905-4. Retrieved August 25, 2013.
179. Reed, E. J. (1997). "Criminal Law and the Capacity of Mentally Retarded Persons to Consent to Sexual Activity". Virginia Law Review. 83 (4): 799–827. doi:10.2307/1073749. JSTOR 1073749.
180. Francoeur RT, Noonan RJ, Opiyo-Omolo B (2004). The Continuum Complete International Encyclopedia of Sexuality. Continuum International Publishing Group. p. 173. ISBN 978-0826414885. Retrieved April 30, 2013.
181. Ken Plummer (2002). Modern Homosexualities: Fragments of Lesbian and Gay Experiences. Routledge. pp. 187–191. ISBN 978-1134922420. Retrieved August 24, 2013. [S]ome sexual practices are regarded as inherently better (normal, natural, more satisfying) than others, with vaginal intercourse privileged as the 'Real Thing.' Such beliefs, influenced by views about sex as ultimately a reproductive function, continue to be perpetuated through discourses on sex despite a number of important contradictions.
182. "An Updated Definition of Rape (U.S. Dept of Justice, January 6, 2012)". Archived from the original on March 13, 2012. Retrieved October 30, 2014.
183. "U.S. to Expand Rape Definition in Crime Statistics (New York Times, January 6, 2012)".
184. Smith, Merril D., ed. (2004). Encyclopedia of rape (1st ed.). Westport, Conn.: Greenwood Press. pp. 169–170. ISBN 978-0-313-32687-5.
185. "Dr James Roffee". Monash university. Archived from the original on February 4, 2017. Retrieved May 22, 2017.
186. Roffee, J. A. (2014). No Consensus on Incest? Criminalisation and Compatibility with the European Convention on Human Rights, doi:10.1093/hrlr/ngu023.
187. Diagnostic and Statistical Manual of Mental Disorders: DSM-IV. Washington, DC: American Psychiatric Association. 2000. ISBN 978-0-89042-025-6.
188. Milner JS, Dopke CA (2008). "Paraphilia Not Otherwise Specified: Psychopathology and theory". In Laws DR, O'Donohue WT (eds.). Sexual Deviance, Second Edition: Theory, Assessment, and Treatment. New York: The Guilford Press. pp. 384–418. ISBN 978-1-59385-605-2.
189. Seto, MC; Barbaree HE (2000). "Paraphilias". In Hersen M; Van Hasselt VB (eds.). Aggression and violence: an introductory text. Boston: Allyn & Bacon. pp. 198–213. ISBN 978-0-205-26721-7.
190. Abigail Perdue; Randall Lockwood (2014). Animal Cruelty and Freedom of Speech: When Worlds Collide. Purdue University Press. pp. 6–8. ISBN 978-1557536334. Retrieved December 9, 2014.
191. Margaret Monahan Hogan (2002). Marriage as a Relationship: Real and Rational. Marquette University Press. p. 88. ISBN 978-0874626575. Retrieved September 1, 2015.
192. James G. Dwyer (2001). Religious Schools V. Children's Rights. Cornell University Press. pp. 72–73. ISBN 978-0801487316. Retrieved August 31, 2015.
193. Ronald Green (2013). Religion and Sexual Health: Ethical, Theological, and Clinical Perspectives, Volume 1 of Theology and Medicine. Springer Science & Business Media. p. 112. ISBN 978-9401579636. Retrieved August 31, 2015.
194. Heather Brook (2015). Conjugality: Marriage and Marriage-like Relationships Before the Law. Palgrave Macmillan. pp. 71–73. ISBN 978-1137480910. Retrieved August 31, 2015.
195. Suzanne K. Steinmetz; Marvin B. Sussman (2013). Handbook of Marriage and the Family. Springer Science & Business Media. pp. 787–788. ISBN 978-1461571513. Retrieved August 31, 2014.
196. Oshisanya, 'lai Oshitokunbo (2015). An Almanac of Contemporary Judicial Restatements (Criminal & Quasi Criminal Law & Procedure) vol. iii: Almanac vol. iii. Almanac Foundation. p. 132. ISBN 978-9785120035. Retrieved August 31, 2015.
197. James A. Brundage (2009). Law, Sex, and Christian Society in Medieval Europe. University of Chicago Press. pp. 609–611. ISBN 978-0226077895. Retrieved August 31, 2015.
198. Philip Carlan; Lisa S. Nored; Ragan A. Downey (2011). An Introduction to Criminal Law. Jones & Bartlett Publishers. p. 139. ISBN 978-1449647216. Retrieved August 31, 2015.
199. "Can Iran 'control' its cohabiting couples?". BBC News. December 10, 2014. Retrieved August 31, 2015.
200. "Amnesty International Report 2014/15". amnesty.org. 2014. Retrieved August 31, 2015.
201. "Share of live births outside marriage". europa.eu. March 2, 2015. Retrieved August 31, 2015.
202. Choudhri, Nihara K (2004). The complete guide to divorce law. New York: Citadel Press. pp. 8–9. ISBN 978-0-8065-2528-0. Retrieved August 30, 2015.
203. "Blanchflower v. Blanchflower and Mayer". Gay & Lesbian Advocates & Defenders (GLAD). December 31, 2003. Retrieved August 9, 2013.
204. "IN THE MATTER OF DAVID G. BLANCHFLOWER AND SIAN E. BLANCHFLOWER". New Hampshire Judicial Branch/courts.state.nh.us. November 7, 2003. Retrieved August 9, 2013.
205. Janet Afary. Sexual Politics in Modern Iran. (2009) Cambridge University Press. ISBN 0-521-89846-3
206. "PUBLIC AI Index: MDE 13/010/2008. UA 17/08 Fear of imminent execution/ flogging". Amnesty International. Archived from the original on March 5, 2016. Retrieved December 22, 2013.
207. Naomi R. Cahn; June Carbone (2010). Red families v. blue families: legal polarization and the creation of culture. Oxford University Press US. p. 129. ISBN 978-0-19-537217-5. Retrieved July 29, 2011.
208. Donald J. Cantor (2006). Same-sex marriage: the legal and psychological evolution in America. Wesleyan University Press. pp. 1–191. ISBN 978-0-8195-6812-0. Retrieved July 29, 2011.
209. American Psychological Association (2004). "Resolution on Sexual Orientation and Marriage" (PDF). Retrieved September 1, 2015.
210. Daniel L. Akin (2003). God on Sex: The Creator's Ideas About Love, Intimacy, and Marriage. B&H Publishing Group. pp. 1–291. ISBN 978-0805425963. Retrieved October 21, 2015.
211. Dennis P. Hollinger (2009). The Meaning of Sex: Christian Ethics and the Moral Life. Baker Academic. pp. 30–33. ISBN 978-0801035715. Retrieved December 9, 2014.
212. Chad Denton (2014). The War on Sex: Western Repression from the Torah to Victoria. McFarland. pp. 107–117. ISBN 978-0547204888. Retrieved December 9, 2014.
213. Margaret D. Kamitsuka (2010). The Embrace of Eros: Bodies, Desires, and Sexuality in Christianity. Fortress Press. pp. 16–17. ISBN 978-1451413519. Retrieved December 9, 2014.
214. Stefanie Knauss (2014). More Than a Provocation: Sexuality, Media and Theology. Vandenhoeck & Ruprecht. p. 69. ISBN 978-3525604502. Retrieved December 9, 2014.
215. Robert G. Barnes; Rosemary J. Barnes (1996). Great Sexpectations: Finding Lasting Intimacy in Your Marriage. Zondervan. p. 66. ISBN 978-0310201373. Retrieved December 9, 2014.
216. Christo Scheepers (2012). Between the Covers: Sexual freedom through the bond of marriage. Struik Christian Media. p. 53. ISBN 978-1415320563. Retrieved December 9, 2014.
217. Jill Oliphant (2010). OCR Religious Ethics for AS and A2. Routledge. p. 213. ISBN 978-1136992919. Retrieved September 1, 2015.
218. D. L. d'Avray (2010). Rationalities in History: A Weberian Essay in Comparison. Cambridge University Press. pp. 177–178. ISBN 978-1139490504. Retrieved September 1, 2015.
219. William H. Swatos; Peter Kivisto (1998). Encyclopedia of Religion and Society. Rowman Altamira. p. 464. ISBN 978-0761989561. Retrieved December 9, 2014.
220. Chase, Stacey (July 23, 2006). "The Last Ones Standing". The Boston Globe.
221. Laura J. Zilney; Lisa Anne Zilney (2009). Perverts and Predators: The Making of Sexual Offending Laws. Rowman & Littlefield. pp. 7–8. ISBN 978-0742566248. Retrieved December 9, 2014.
222. Don S. Browning, Martha Christian Green, John Witte. Sex, marriage, and family in world religions. (2006) Columbia University Press. ISBN 0-231-13116-X
223. Abdul Rahman bin Abdul Karim al-Sheha. Islamic Perspective of Sex (2003) Saudi Arabia. ISBN 9960-43-140-1
224. Fatima M. D'Oyen. The Miracle of Life. (2007) Islamic Foundation (UK). ISBN 0-86037-355-X
225. Joseph, Suad; Naǧmābādī, Afsāna (2003). Encyclopedia of Women and Islamic Cultures: Family, Law and Politics. BRILL. p. 454. ISBN 9789004128187.
226. al-Qaradawi, Yusuf (2013). The Lawful and the Prohibited in Islam: الحلال والحرام في الإسلام. The Other Press. p. 20. ISBN 9789670526003.
227. Simon, Rita James; Brooks, Alison (2009). Gay and Lesbian Communities the World Over. Rowman & Littlefield. p. 17. ISBN 9780739143643.
228. Harvey, Peter. An Introduction to Buddhist Ethics: Foundations, Values and Issues. Cambridge, 2000: 71-72.
229. Harvey, Peter. An Introduction to Buddhist Ethics: Foundations, Values and Issues. Cambridge, 2000: 71-74.
230. Kenneth E. Bowers. God Speaks Again: An Introduction to the Baha'i Faith. (2004) Baha'i Publishing. ISBN 1-931847-12-6
231. John A. Buehrens and Forrest Church. A Chosen Faith: An Introduction to Unitarian Universalism. (1998) Beacon Press. ISBN 0-8070-1617-9
232. Hodgkinson, Liz (2002). Peace and Purity: The Story of the Brahma Kumaris a Spiritual Revolution. HCI. pp. 2–29. ISBN 978-1-55874-962-7.
233. Babb, Lawrence A. (1987). Redemptive Encounters: Three Modern Styles in the Hindu Tradition (Comparative Studies in Religion and Society). Oxford University Press. ISBN 0-7069-2563-7. "Sexual intercourse is unnecessary for reproduction because the souls that enter the world during the first half of the Cycle are in possession of a special yogic power (yog bal) by which they conceive children."
234. Barrett, David V (2001). The New Believers. Cassell & Co. pp. 265. ISBN 0-304-35592-5.
235. Thompson, Lady Gwen; Wiccan-Pagan Potpourri; Green Egg, №69; Ostara 1974
236. Hans Holzer. The Truth about Witchcraft (1971) Doubleday. page 128. ISBN 0-09-004860-1
237. Baba, Meher (1995). Discourses. Myrtle Beach: Sheriar Press. p. 109. ISBN 9781880619094.
238. William Skudlarek. Demythologizing Celibacy: Practical Wisdom from Christian and Buddhist Monasticism. (2008) Liturgical Press. ISBN 0-8146-2947-4
239. Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). "Chelicerata: Araneae". Invertebrate Zoology (7th ed.). Brooks/Cole. pp. 571–584. ISBN 978-0-03-025982-1.
240. Cecie Starr; Christine Evers; Lisa Starr (2010). Cengage Advantage Books: Biology: A Human Emphasis. Cengage Learning. pp. 630–631. ISBN 978-1133170051. Retrieved December 9, 2010.
241. Edward J. Denecke Jr. (2006). New York State Grade 8 Intermediate Level Science Test. Barron's Educational Series. p. 105. ISBN 978-0764134333. Retrieved December 9, 2014.
242. M. Yadav (2003). Breeding in Insects. Discovery Publishing House. p. 59. ISBN 978-8171417377. Retrieved December 9, 2014.
243. Franz Engelmann (2013). The Physiology of Insect Reproduction: International Series of Monographs in Pure and Applied Biology: Zoology. Elsevier. pp. 58–59. ISBN 978-1483186535. Retrieved December 9, 2014.
244. Janet Leonard; Alex Cordoba-Aguilar (2010). The Evolution of Primary Sexual Characters in Animals. Oxford University Press. p. 334. ISBN 978-0199717033. Retrieved December 9, 2014.
245. P. J. Gullan; P. S. Cranston (2009). The Insects: An Outline of Entomology. John Wiley & Sons. p. 124. ISBN 978-1405144575. Retrieved December 9, 2014.

External links

• The International Encyclopedia of Sexuality
• Glossario di Sessuologia clinica – Glossary of clinical sexology
• Janssen, D. F., Growing Up Sexually. Volume I. World Reference Atlas
• Introduction to Animal Reproduction
• Advantages of Sexual Reproduction
• Synonyms for sexual intercourse – the WikiSaurus list of synonyms and slang words for sexual intercourse in many languages