Abstract: We found 22 trials that evaluated pericoital use of LNG and other hormonal drugs on a regular basis to prevent pregnancy. The studies included a total of 12,400 participants, and were conducted in Europe, Asia, and the Americas. The drugs and doses evaluated included levonorgestrel (LNG) 0.75 mg (11 studies), LNG in doses other than 0.75 mg (4 trials), and hormones other than LNG (7 trials). Outcomes included pregnancy rates, discontinuation, side effects, and acceptability. Pericoital levonorgestrel was reasonably efficacious and safe. The pooled Pearl Index for the 0.75 mg dose of LNG was 5.4 per 100 woman-years (95% CI 4.1 to 7.0). The pooled Pearl Index for all doses of LNG was 5.0 per 100 woman-years (95% CI 4.4 to 5.6). Other hormonal drugs appeared promising but most of them were not studied extensively. Menstrual irregularities were the most common side effects reported. However, the studies provided no consistent evidence of a relationship between bleeding abnormalities and either frequency of pill intake or total dose of the drug. Non-menstrual side effects were reportedly mild and not tabulated in most studies. Most women liked the pericoital method in spite of frequent menstrual irregularities. The studies of pericoital LNG regimens provided promising results but many had serious methodological issues. Most reports were decades old and provided limited information. However, we considered the evidence to be moderate quality because of the large number of participants from diverse populations, the low pregnancy rates, and the consistent results across studies. Rigorous research is still needed to confirm the efficacy and safety of pericoital use of LNG as a primary means of contraception among women with infrequent intercourse. If the method is shown to be efficacious, safe and acceptable, the results may warrant revision of the current World Health Organization recommendations and marketing strategies.

Plain-language summary: We ran computer searches until 1 September 2014 to find relevant studies in any language. For the initial review, we also wrote to researchers to find other trials. We assessed the quality of the research methods in the studies. We used the Pearl Index to estimate the effect. The Pearl Index is the number of pregnancies for every 100 years of pill use. We found 22 studies from the past 40 years. They included a total of 12,400 women in Europe, Asia, and the Americas. Fifteen trials studied different doses of the hormone levonorgestrel and seven looked at other hormones. These studies showed that using some hormones right before or after sex did prevent pregnancy. Levonorgestrel seemed to work well, and was safe and accepted by thousands of women in several large trials. The most common side effects were menstrual bleeding problems. However, such bleeding issues were not always related to how often women took the pills or the total dose of the drug. Most studies were old and many reports were not complete. However, the data had moderate quality because of the many women in these studies, the low pregnancy rates, and the consistent results. We do not know for sure whether using levonorgestrel repeatedly around the time of sex is a good and safe method of birth control. More high-quality research is needed to answer the question.