How Effective Is Emergency Contraception?

The most widely used pill regimen for emergency contraception involves two doses of high-dose oral contraceptives -- one within 72 hours of unprotected coitus and another 12 hours later. Each dose consists of two OCs, each containing 50 μg of ethinyl estradiol and 0.5 mg of norgestrel. Does this method work? This article pooled results from 10 observational trials.

Reported failure rates ranged from 0.2% to 2.8%, and loss to follow-up varied from 0.0% to 22.7%. Though the pooled rate of pregnancy was 1.5% (95% CI, 1.2%-1.9%), nine studies had failure rates outside this range, suggesting that the probability of failure varies. The authors argue that a better measure is the reduction in the risk of conception, which factors in the cycle day on…