Interception : the use of postovulatory estrogens to prevent implantation

In the 60s and 70s, Morris and van Wagenen tested how diethylstilbestrol could prevent implantation in macaque monkeys


…”Nonetheless, clinical experience has been encouraging in both reported and unreported series of cases. To quote Haspels,’

“The administration of large doses of estrogen to 2,000 women during the first five days after unprotected intercourse is found to be effective in reducing the incidence of pregnancy to a very low level.”

Failures have been in most instances related to errors in timing or inadequate dosage of estrogen. Compounds that have been used in women include diethylstilbestrol, 25 to 50 mg. per day; diethylstilbestrol diphosphate (Stilphostrol*) , 50 mg. per day; ethinyl estradiol, 1 to 5 mg. per day : and conjugated estrogens (Premarinf ), 20 to 25 mg. per day. “…

…”Based on the macaque studies, stilbestrol given in a dose of 50 mg. per day for 6 days en in a dose of 50 mg. per day for 6 days should be an effective interceptive, or a total dose of approximately 200 to 300 mg. for the average woman. Of 15 women who became pregnant after postcoital stilbestrol or stilbestrol diphosphate, 8 received total doses of 30 to 150 mg. Several of these involved multiple exposures and questions of timing as well. In 7 receiving 250 mg., there were 2 treated on the twenty-second and twenty-ninth days of the cycle, and 2 had multiple exposures and the time of ovulation was uncertain. In 3 patients, the dosage (250 mg.) and timing seemed correct, and they must be listed as method failures.”…

…”Only one case involving a serious side effect has been observed, SchumacheF at Miami University reported a student who developed findings compatible with acute pulmonary edema after 3 doses of stilbestrol (50 mg. per day). She had given a history of fluid retention prior to her period. With oxygen and supportive therapy, the chest cleared completely within 36 hours.”…


  • Interception: the use of postovulatory estrogens to prevent implantation, American journal of obstetrics and gynecology, NCBI PubMed PMID: 4628937, 1973 Jan.
  • Image credit Jonathan Forage.

Have your say! Share your views