OBJECTIVE:

The objective of this study was to describe bleeding after use of an emergency contraceptive pill (ECP) regimen consisting of 1.5 mg of levonorgestrel in a single dose.

METHODS:

We asked 120 women who had been treated with the regimen to keep daily bleeding diaries for 9 weeks. We compared bleeding patterns observed after treatment with usual patterns reported by the participants and with patterns observed in a prior study on women who had not taken ECPs.

RESULTS:

Treatment in the first 3 weeks of the menstrual cycle significantly shortened that cycle as compared both with the usual cycle length and with the cycle duration in a comparison group. The magnitude of this effect was greater the earlier the pills were taken. In contrast, the duration of the first menstrual period after treatment increased significantly with cycle week of treatment and was longer in women who used the treatment than in those who did not. Intermenstrual bleeding occurred in only 5% of women in the first cycle after treatment.

CONCLUSIONS:

The effect of the single-dose levonorgestrel ECP regimen on the timing and duration of the next menstrual period depends on when during the cycle the pills are taken. Intermenstrual bleeding following treatment is uncommon.