Changes in menstrual cycle length and regularity after use of oral contraceptives.

This is an analysis of changes in menstrual cycle length and regularity occurring for a group of 211 women who had discontinued use of oral contraceptives. The analysis is based on prospectively recorded histories from the Menstruation and Reproduction History Program. Post-pill menstrual cycle length and regularity are compared with pre-pill averages. In the first post-pill cycle, there was an average increase of 6 days in cycle length. In subsequent cycles, however, cycle length and regularity were comparable to pre-pill norms in most cases.