Conception delay after oral contraceptive use: the effect of estrogen dose.

A significant delay was observed in conception among 248 former oral contraceptive (OC) users compared with women discontinuing other methods of contraception (n = 1,365). The mean time to conception was 5.88 cycles (95% confidence interval [CI] 5.38, 6.38) for former OC users and 3.64 cycles (95% CI 3.49, 3.79) after other contraceptives. Women discontinuing OCs with higher doses of estrogen (greater than or equal to 50 micrograms) had greater conception delays than those on lower estrogen doses who, in turn, had longer delays than other method users. Oral contraceptive use was associated with significant reductions in conception for each of the first six cycles after discontinuation. This study provides further evidence for a direct effect of oral contraception on delayed conception, suggests that the delay lasts longer than previously thought, and finds that the probability of conception after OC discontinuation depends on the estrogen dose of the OC.