Emergency contraception: methods and efficacy.

A number of effective and safe methods for emergency contraception are now available. High doses of oestrogens, although effective, are seldom used nowadays because of the high incidence of nausea and vomiting, and the need for administration for 5 days. The Yuzpe regimen, consisting of administration of two doses of combined oral contraceptive pills with a 12-h interval, can prevent more than 74% of expected pregnancies, but the incidence of side effects, mainly gastrointestinal side effects, is high. Levonorgestrel and mifepristone are more effective than the Yuzpe regimen and have a lower incidence of side effects. They can prevent about 85% of pregnancies. The efficacy of both the Yuzpe regimen and levonorgestrel decreased with increase in the intercourse-treatment interval. The dose of mifepristone can be reduced to 10 mg without loss of efficacy. Both levonorgestrel or mifepristone are not yet widely available, and the Yuzpe regimen remains the only hormonal method in many countries. The postcoital insertion of an intrauterine contraceptive device is also a highly effective method, which can prevent over 90% of pregnancies.