Levonorgestrel and mifepristone in emergency contraception.

Research on new technologies by the Special Programme of Research, Development and Research Training in Human Reproduction at WHO has led to the development of two new methods for emergency contraception, the levonorgestrel regimen and a low-dose mifepristone regimen. In 4 years, the levonorgestrel regimen has already been approved in some 95 countries. We review this research and present combined data from our multinational trials and combined estimates of efficacy for mifepristone and for levonorgestrel separately. Data were available for 6283 women in 10 mg mifepristone groups and 4098 women in levonorgestrel groups. One of these studies compared the two methods, namely a randomized, double-blind trial in which we also investigated a single dose of 1.5 mg of levonorgestrel. Both levonorgestrel and mifepristone are effective for emergency contraception and prevent a high percentage of pregnancies when used within a few days after coitus. Mifepristone is associated with later return of menses compared to levonorgestrel.