Are there two types of postpill anovulation?

Anovulation, indicated by requiring treatment with clomiphene or gonadotropins to conceive, was studied in a cohort of 16,583 women interviewed postpartum. There were 2,853 former oral contraceptive users, and 2.2% of them reported anovulation, compared with 2.7% of controls. Among primigravidas, the rates were 4.2% and 4.4% in pill users and controls, respectively. A statistically significant excess of anovulation was reported by former pill users who had been underweight in relation to their height at the time of conception. Independently of pill use, the condition tended to be associated with obesity. Data from this and previous studies suggest that there may be two distinct entities of postpill anovulation: the first, identical with spontaneous secondary anovulation; the second, occurring in slender women who have used oral contraceptives. These findings need confirmation from prospective studies using standard diagnostic criteria.