Because hormonal contraception is the only type that actually suppresses a physiological function, ovulation, the question of reversibility is particularly acute. A large proportion of pill users are young women who have not completed, and may not have started, their families. The 1974 Royal College of General Practitioners Study of 2291 women stopping oral contraceptives to become pregnant indicated that after 1 year, 19% of nulliparas and 10% of multiparas had not conceived. The peak of conceptions occurred in the 3rd month, suggesting a slight but transient fertility decline. The lack of controls limited the conclusions of the study. A 1978 British study of 3898 women showed that nulliparas stopping pill use experienced a longer time to conception than did those stopping condom use, but the difference disappeared after 7 months. However, the study was retrospective and the interviews occurred several years after the pregnancies. A study of 1403 women who had used pills and 4477 who had used other methods showed that through the 6th month, the number of former pill users who had not conceived was higher, especially among older women and longterm pill users. This too was a retrospective study and excluded infertile couples. The prospective study by the Oxford Family Planning Association of 17,000 women showed a significant diminution in the fertility of women stopping OC use compared to those using the diaphragm who had never used the pill, but the difference diminished with time and was negligible after 3 years. No relationship to duration of pill use was described. A study of 1157 women in Paris conducted in 1978-80 showed a similar delay. Despite methodological problems, the studies are unanimous in suggesting a temporary diminution of fertility among women who have used the pill. Although few studies have been done, it appears that 95% of women resume ovulation within 3 months of discontinuing pill use. Postpill amenorrhea, which occurs in about 1.2% of cases, is apparently the outcome of fertility problems that predated the use of OCs.