THE EFFECT OF LARGE DOSES OF ESTROGENS POST COITUM IN 2000 WOMEN

Abstract The administration of large doses of estrogens to 2000 women during the first 5 days after unprotected intercourse was found to be effective in reducing the incidence of pregnancy to a very low level. We personally prescribe only the maximum dosage of 5 mg ethinylestradiol or 50 mg diethylstilbestrol starting within 24–36 hours post coitum, under which regimen we have not observed a single pregnancy thus far. The basal temperature curve showed a decrease in temperature to preovulatory values. Implantation of the ovum in the uterus is probably prevented by accelerated expulsion of the ovum and/or endometrial changes. Impairment of the production and/or the release of progesterone from the corpus luteum could also play a role. Side effects such as nausea and vomiting can be reduced by administration of an antiemetic. Subsequent unprotected intercourse during the same cycle should be discouraged. The fact that pregnant women excrete large amounts of estrogens indicates the theoretical likelyhood that the period during which estrogens can be effective, will be relatively short. As vaginal cancer has been described in children of about 15 years old of mothers who used diethylstilbestrol in large quantities during their pregnancy we recently decided to prescribe only 5 mg ethinylestradiol for 5 days.