an oral drug that, when taken by a woman within 2-3 days after intercourse, reduces the probability that she will become pregnant. SYN: emergency hormonal contraception, postcoital contraception.The U.S. Food and Drug Administration (FDA) has approved two regimens for postcoital contraception. The Yuzpe regimen consists of a combination of progestogen (levonorgestrol 0.25 mg or norgestrel 0.5 mg) and estrogen (ethinyl estradiol 100 mcg) taken at once and repeated in 12 hours. Alternatively, two doses of levonorgestrel 0.75 mg may be taken without estrogen. With either regimen, the first dose should preferably be taken within 24 hours after intercourse, and not more than 72 hours after. The Yuzpe method reduces the likelihood of pregnancy by about 57%, the levonorgestrel method by 85%. About 50% of women experience uterine bleeding within 1 week and most of the rest within 3 weeks unless conception has occurred. If taken early enough, the hormones may prevent fertilization by altering tubal function or exerting toxicity against the ovum. Probably, however, they usually act by preventing implantation of a fertilized ovum. This is not emergency contraception but rather chemical abortion. The incidence of nausea is about 40% with levonorgestrel alone and about 65% with the Yuzpe regimen. Headache, fluid retention, and breast tenderness may also occur. This procedure is contraindicated in women for whom oral contraceptives are contraindicated, such as those with hypertension or a history of stroke or thromboembolic disease. The short course of high-dose hormones probably does not interrupt a pregnancy after implantation has occurred, and there is no evidence that fetal harm has occurred when such a pregnancy has continued to term. However, hormone use is contraindicated in known pregnancy or if the woman has had unprotected intercourse within the preceding 3-10 days. An application for over-the-counter marketing of levonorgestrel has been denied by the FDA.