Conception-waits in fertile women after stopping oral contraceptives.

Conception-waits were studied retrospectively in 1,403 fertile oral contraceptive users who had stopped medication in order to conceive, and in 4,477 controls who stopped using other contraceptives. The proportion of pill users who conceived in the first month was 30% less than the others, but by the third month this difference had disappeared. There was no excess of long conception-waits in the oral contraceptive group nor any evidence for a cyclic return of fertility in them. There was a highly significant interaction between pill use and age, older women having a greater degree of temporary reduction in conceptions shortly after stopping the pill. There was also an interaction involving age and duration of use. In women who had used the pill for a short time, there was little age-effect, and in younger women there was little effect of the duration of use. Older women who had used the pill for several years, however, had a marked temporary reduction in fertility on stopping it.