Abstract

PIP: A retrospective study of the delay in conception after stopping different methods of contraception is undertaken among 5108 pregnant women residing in a departement in the Paris region. Particular attention is paid to the delay that sometimes separates the cessation of contraception and the beginning of intercourse without precautions. The counfounding factors considered are: the observation of a waiting period following cessation of contraception; the existence of a strategy, i.e., a coital pattern adopted by certain couples who have intercourse more often during the middle of the cycle, hoping to conceive more rapidly; the regularity of the menstrual cycle and the woman's age at the beginning of unprotected intercourse. The statistical techniques include chi-square analysis, analysis of variance correlation, partial multiple regression and actuarial rates of infecundity. The mean age of women at their last period was 26.3 years; 37.6% were primagravida; 87.3% worked outside the home and 36.6% were smokers. 72% of the women used oral contraceptives; 14% the IUD, and 14% other methods. Among all factors studied, 4 are strongly related both to fertility and to mode of contraception: the waiting period, coital strategy, regularity of the menstrual cycle and the woman's age. Shorter average time required to conceive (TRC) and greater fecundability are associated with the observation of a waiting period, no coital strategy, and regular cycles. The woman's age at the time of unprotected intercourse shows no correlation with TRC; it does, however, show a correlation with fecundability, which increases with age to reach a maximum in the age group 25-29 and then decreases progressively. These 4 factors are also related to the mode of contraception. Those using hormonal contraception were more likely to observe a waiting period. However, they report a coital strategy less frequently, their usual cycle is more often irregular and they are younger than IUD or other method users. Results demonstrate a decreased fertility for couples after the pill and, to a lesser degree, after IUD use, but only among those who did not take other precautions (waiting period). For couples observing a waiting period, there is no decrease of fertility following the initial exposure to the risk of conception. This comparison of return of fertility following cessation of different contraceptive methods shows that raw data must be interpreted with caution. It is essential to take into account the possibility of delay in becoming exposed to the risk of conception while various confounding factors must also be considerd.