Influence of copulation on time of ovulation in women

Abstract

Data from animal studies and clinical literature suggesting that coitus-induced ovulation may occur in women is reviewed. Although a spontaneous ovulator the rat has displayed ovulation following coitus with a rise in plasma LH 5 to 10 minutes after intercourse and it has been shown that reflex ovulation in the rat is a function of the intensity of vaginal and cervical stimulation. Direct evidence evidence of spontaneous human ovulation at midcycle (range 8 to 10 days) has been found while other studies indicate that ovulation may occur during any day of the menstrual cycle and that copulation may be the initiator of the response. Conception following rape has been found to occur at any stage. The intensity of coitus during rape is likely to be greater than normal coitus and this increased intensity could be an important factor in human reflex ovulation. Coitus-induced ovulation may be a factor in the observed failures of the rhythm method. Menstrual cycle length in both monkeys and women is extremely variable (24 to 38 days for humans) but it is generally agreed that the postovulatory period is fairly constant with an average length of 14 days. Coitus-induced ovulation early in the cycle would produce a short cycle and long cycles would result if reflex ovulation occurred later in the preovulatory phase. Research of rhesus monkeys kept isolated from males revealed that only 50% ovulated. If women were similarly isolated the number showing anovulatory cycles might increase considerably. Studies of human ovulation should include records of the effects of coital activity and its influence on results.