Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception.
A previous study suggested that provision of two 0.75 mg doses of levonorgestrel for emergency contraception caused less nausea and vomiting and was more effective than the Yuzpe regimen of combined oral contraceptives (two doses of 100 mcg of ethinyl estradiol and 0.5 mg of levonorgestrel). These two regimens were evaluated further in a double-blind, randomized World Health Organization study of 1998 women recruited from 21 centers worldwide who requested emergency contraception within 72 hours of unprotected intercourse. Among the 1955 women for whom the outcome was known, the crude pregnancy rate was 1.1% (11/976) in the levonorgestrel group and 3.2% (31/979) in the Yuzpe group. The crude relative risk of pregnancy for levonorgestrel compared with the Yuzpe regimen was 0.36 (95% confidence interval, 0.18-0.70). The proportion of pregnancies prevented was 85% in the former group and 57% in the latter group. Nausea and vomiting occurred significantly less frequently in the levonorgestrel group (23.1% and 5.6%, respectively) than in the Yuzpe regimen group (50.5% and 18.8%, respectively). The efficacy of both treatments declined significantly (p = 0.01) with increasing time since unprotected intercourse. These findings confirm that the levonorgestrel regimen may be more effective and is better tolerated than the current standard in emergency contraception.