Late postcoital treatment against pregnancy with antiprogesterone RU 486

Thirty female volunteers who had experienced an occasion of unprotected intercourse in midcycle were given a single oral dose of 600 mg of RU 486 1 day before the expected onset of menses. Eighteen of them (60%) had conceived, as evident by human chorionic gonadotropin elevation (greater than 2 IU/L). Menstrual-like bleeding was induced in 29 women (97%). Only one woman became clinically pregnant, and this pregnancy was subsequently terminated by vacuum aspiration and curettage. The drug treatment was well tolerated, but it lengthened the post-treatment menstrual cycle on average by 4 days. RU 486 thus may offer an alternative for postcoital prevention of pregnancy if taken before the establishment of menses delay. The lengthening of the first post-treatment cycle may invalidate the use of RU 486 as a regular once-a-month contraceptive.