Hormonal postcoital contraception

Abstract

Wide availability of hormonal postcoital contraception (HPC) is likely to reduce the incidence of unplanned pregnancies. The two most common indications for HPC are unprotected intercourse and 'condom accidents'. The combined estrogen/progestogen HPC described by Yuzpe is the most widely used method. It is given within 72 h of unprotected intercourse. The efficacy of combined HPC is high. The crude failure rate is 1-5 per 100 woman-months while the true reduction in pregnancy risk is over 75%. Efficacy is not influenced by the exposure-treatment interval within the 72-h 'window'.The mechanism of action is multifocal and depends on the cycle phase at which treatment is instituted. Data are presented suggesting a consistent endometrial effect. None of the side-effects of HPC are serious. When HPC fails, there is so far no evidence of an adverse effect of the treatment on the outcome of pregnancy. Counselling should include all the above together with discussion of possible side-effects such as nausea and vomiting. The clinician should ensure that the woman uses an effective contraceptive thereafter. There is renewed interest in progestogen-only postcoital contraception. Varying doses of levonorgestrel have been used. The efficacy of some regimens is similar to that of the combined HPC. Danazol has not proved to be as effective. Antiprogestins hold the greatest promise of emergency contraception with high efficacy and low side-effects.