Coitus-induced ovulation

Evidence of coitus-induced ovulation in humans is reviewed and there is a need for further biochemical statistical and demographic analyses of the frequency and sociologic importance of coitomimetic stimuli in humans.

Abstract

This article reviews evidence of coitus-induced ovulation. Maintenance of reproductive efficiency by more than 1 mechanism for triggering ovulation is interpreted as an evolutionary phenomenon aimed at ensuring the survival of the species. In earlier research estrogen levels or progesterone output were believed to regulate the ovulatory luteinizing hormone (LH) release and the length of the receptive period in spontaneous ovulators; more recently the effect of neural olfactory and emotional stimuli has been recognized. The neuroendocrine systems involved in spontaneous and reflex-induced ovulation include the hypothalamic-hypophyseal-gonadokinetic system and the neurohormonal pathways for coitomimetic stimuli. In spontaneously ovulating rodents the stimulus of coitus serves as an inducer for pseudopregnancy. The translation of vaginal stimulation into gonadomimetic humoral messages released from the hypothalamus and/or the posterior pituitary for the liberation of LH and prolactin is not completely understood. Nervous or biochemical influences resulting from coitus may even more directly affect ovarian functions by local sympathetic reflexes or by biochemical components of the ejaculate. In coitus-induced ovulation central nervous and/or peripheral autonomic nervous involvement may interact to push ovarian follicles toward maturation and ovulation or may help to ovulate nearly ripe or ripe follicles as a result of cohabitation. Acceptance of coitus-induced ovulation in humans renders rhythm methods of fertility control unreliable. In 1 large study of pregnancies resulting from rape 33-46% of conceptions occurred during what should have been a safe period. Emotions may also play a role in facilitating or predisposing to coitus-induced ovulation. There is a need for further biochemical statistical and demographic analyses of the frequency and sociologic importance of coitus-induced ovulation in humans.