Emergency contraception with levonorgestrel or the Yuzpe regimen.
In response to concerns raised by both Trussell and Ellertson et al., the authors (members of the WHO Task Force on Postovulatory Methods of Fertility Regulation) investigated the impact of time elapsed since unprotected intercourse on the efficacy of emergency contraception in more detail. Overall, the pregnancy rate increased from 0.5% when treatment was initiated within 24 hours to 4.1% after a time lapse of 61-72 hours. Postponement of the first dose by 12 hours increased the likelihood of pregnancy by almost 50%. A levonorgestrel-only regimen was consistently more effective than the Yuzpe regimen. A comparison of the pregnancy risk associated with levonorgestrel with that of Yuzpe in the 7 studies pooled by Trussell yields a relative risk of 0.3 (95% confidence interval, 0.23-0.97)--similar to that reported in the WHO study with other conception probabilities. Since the Yuzpe regimen has not been updated since 1973, it is time to review and improve emergency contraception options.