WHY DO WOMEN HAVE ORGASMS?
It is generally accepted that female orgasms are not essential for reproduction, and any benefit that they may have for female biology is, as yet, unclear. Early theorists believed that orgasm via intercourse activated ovulation and closed off the womb to air, thus facilitating conception (28). When it was later shown that the human female was a spontaneous ovulator at mid-cycle, and that this was unconnected to coitus, the discourse re-focused on the role of uterine suction created by orgasmic contractions in moving ejaculated spermatozoa through the cervix into the uterus and then fallopian tubes. However, there is now good evidence that the fastest transport of spermatozoa into the human uterus is actually in the sexually unstimulated condition (29).
An essential feature of sexual arousal of the female genitalia is to create the expansion of the vagina (vaginal tenting) and elevation of the uterocervix from the posterior vaginal wall. This reduces the possibility of the rapid entry of ejaculated spermatozoa into the uterus and gives time for the initiation of the decoagulation of semen and the capacitation of the spermatozoa to begin, decreasing the chance of incompetent sperm being transported too rapidly into the fallopian tubes (29). By dissipating arousal and initiating the resolution of the tenting, orgasm may allow the earlier entry of the spermatozoa into the cervical canal and their subsequent rapid transport to the fallopian tubes.
It has been suggested that women may use orgasm, initiated either from coitus or masturbation, as a way to manipulate the ejaculate in the vagina (30,31). This highly contentious concept is based on the amount of “flowback” (semen/fluid) lost from the vagina. The claim is that the amount of flowback con- taining spermatozoa varies with the precise timing of the woman’s orgasm in relation to the time of deposition of the ejaculate into the vagina. Low sperm retention is thought to be associated with female orgasms that occur less than 1 min before vaginal deposition while maximum retention is thought to occur with orgasms occurring shortly after deposition. If orgasm occurs earlier than 1 min before the ejaculate, deposition sperm retention is the same as when there is no orgasm. According to Baker and Bellis (31) the effect of orgasm on sperm retention lasts only for the period of 1 min before semen deposition and up to 45 min later.
An additional function of women’s orgasm, which may play a role in the reproductive process, is that if the woman attains orgasm during coitus, the associated contractions of the vagina can facilitate male ejaculation. This would allow the woman to capture the sperm of her chosen inseminator. In addition, as noted earlier, orgasm increases the secretion of prolactin. If prolactin in plasma is able to enter into the vaginal, cervical or uterine fluids, it may influ- ence the entry of calcium into the sperm and this action could play a role in the activation of spermatozoa in the female tract (32).
There have been a number of other explanations offered for why women have orgasms. Some of those explanations are as follows. To the extent that orgasm is an intensely pleasurable sensation, it serves as a reward for the accep- tance of the danger of coitus with its possibility of pregnancy and of possible death in childbirth. Orgasm serves as a means for resolving pelvic vasoconges- tion and vaginal tenting, and for inducing lassitude to keep the female horizontal and thereby reducing seminal “flowback.” Through both psychological (loss of body boundaries and separateness) and physiological (oxytocin release) means, orgasm may enhance pair bonding. Lastly, by its activation of muscular contractions and the concomitant increased blood flow, orgasms maintain the functionality of the genital tract (33).