Discussions of female orgasm are complicated by the fact that, perhaps artificially, orgasm in women has sometimes been labeled as two different things: the clitoral orgasm and the vaginal orgasm.
The concept of vaginal orgasm as a separate phenomenon was first postulated by Sigmund Freud. In 1905, Freud stated that clitoral orgasm was purely an adolescent phenomenon, and upon reaching puberty the proper response of mature women was a change-over to vaginal orgasms, meaning orgasms without any clitoral stimulation. While Freud provided no evidence for this basic assumption, the consequences of this theory were considerable. Many women felt inadequate when they could not achieve orgasm via vaginal intercourse alone, involving little or no clitoral stimulation, as Freud's theory made man's penis central to a woman's sexual satisfaction.
Women's orgasms have been estimated to last, on average, approximately 20 seconds, and to consist of a series of muscular contractions in the pelvic area that includes the vagina, the uterus and the anus. For some women, on some occasions, these contractions begin soon after the woman reports that the orgasm has started and continue at intervals of about one second with initially increasing, and then reducing, intensity. In some instances, the series of regular contractions is followed by a few additional contractions or shudders at irregular intervals. In other cases, the woman reports having an orgasm, but no pelvic contractions are measured at all.