Delay in conception for former 'pill' users.

Interview data from 3,214 married women having planned pregnancies and singleton deliveries who had no history of fertility treatment and who conceived more than two weeks after cessation of contraception were analyzed. The interval from cessation of contraception to conception was 13 months or greater for 24.8% of prior "pill" users vs 10.6% for former users of all other methods. As compared with former users of other methods, pill users had a notably lower monthly percentage of conceptions for the first three months and somewhat lower percentage from four to ten months. Results were not altered when potential confounding variables were controlled by logistic regression. At least 15 months of unsuccessful trials might be a more appropriate working definition of infertility for previous pill users rather than the 12-month interval generally accepted for this purpose.