Efficacy and side effects of immediate postcoital levonorgestrel used repeatedly for contraception. United Nations Development Programme/ United Nations Population Fund/World Health Organization/World Bank Special Programme of Research, Development and Research Training in Human Reproduction, Task Force on Post-Ovulatory Methods of Fertility Regulation. vonhertzenh@who.ch.

We evaluated the efficacy and side effects of immediate postcoital administration of levonorgestrel 0.75 mg used repeatedly for contraception. A total of 295 healthy women with infrequent coitus were enrolled at 6 study sites. Each woman took levonorgestrel 0.75 mg by mouth immediately after intercourse during 6 months as her only method of contraception. We collected data on side effects and acceptability and calculated the Pearl index failure rates over 133 woman-years of use by standard methods. The Pearl index failure rate was 6.8 (95% CI 3.1-12.9) pregnancies per 100 woman-years of use. The overall probability of pregnancy per treated coital act was 1.4 per 1000. Approximately one-third of participants discontinued the study within 6 months (mainly for bleeding problems). Menstrual complaints were reported by 70% of women. Other complaints included (in decreasing order) nausea, breast tenderness, weakness, dizziness, headache, abdominal bloating, loss of libido, depression, and vomiting. High-dose levonorgestrel pills are unsuitable for regular postcoital contraception.