Post-coital contraception

In the 1960s and 1970s, high doses of DiEthylStilbestrol were used as post-coital contraception ; the morning-after pill

1985 Study Abstract

Current interceptive methods of contraception utilizable between ovulation and nidation include hormonal methods and IUDs. Since the 1st clinical study of the use of high doses of estrogen as a postcoital contraceptive appeared in 1967, the remarkable efficacy of the method has been confirmed by numerous other studies.

The most important series used 50 mg diethylstilbestrol (DES) or 5 mg ethinyl estradiol (EE) per day for 5 days beginning within 72 hours of unprotected intercourse. The mechanism by which estrogens exercise their interception are unclear, but there are probably several factors involved including luteolysis and anomalies in endometrial development. The method is highly effective but rates of nausea, vomiting, breast tenderness, and to a lesser degree menorrhagia are high. The incidence of extrauterine pregnancy is about 1 per 10 intrauterine pregnancies for any postcoital method. Estrogen postcoital contraception is preferable to DES because of the fear of genital adenosis or vaginal adenocarcinoma in case of failure of DES. Opinion is divided as to the teratogenic risks of high doses of estrogens in general.

Postcoital contraception with a progestin, levonorgestrel, which renders the endometrium inhospitable to nidation, was 1st described in 1973. The efficacy of norgestrel alone depends on the dose used. The most common secondary effects are spotting and cycle shortening. The method has the advantage of requiring a very small dose, but the disadvantage of requiring administration in the 12 hours following intercourse. Several combinations of estrogens and progestins have been proposed for postcoital use, of which the most interesting consists of 1 mg of dl-norgestrel and 100 mcg of EE repeated exactly 12 hours later. The treatment should be administered within 12 hours of unprotected intercourse. A multicenter study of 692 women treated with this method gave a pregnancy rate of 1.6%, which would have been lower if 4 women not meeting the conditions of treatment had been excluded. 52.7% of women treated had nausea or vomiting. Compared to estrogens alone, the EE-Norgestrel combination takes less time, requires 4 pills instead of 50 or 60, is better tolerated overall, and requires much less estrogen.

Postcoital insertion of an IUD is very effective and has the advantages that it can be used later than 72 hours following intercourse, it is the only method currently available in case OCs are contraindicated, it allows subsequent longterm effective contraception, and it is 100% effective. The major disadvantages are pain on periovulatory or postovulatory insertion and the risk of infection. Possible future hormonal methods of postcoital contraception based on use of anti-progesterone steroids, especially RU486, or of luteinizing hormone releasing hormone agonist are currently under development.



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