The risk of vaginal cancer among daughters of women who received estrogen during pregnancy has been calculated in the first prospective study reported to date (Lanier, A. P. et al., Mayo Clin. Proc., 48:793, 1973). Among nearly 24,000 children born at the Mayo Clinic obstetrics facilities, 1943 to 1959, no cancers were found among 404 females exposed to synthetic estrogens in the first trimester and traced to 13 to 29 years of age (median, 22 years). From this result it was estimated that the risk of developing vaginal or cervical clear-cell adenocarcinoma was no greater than seven per 1,000 by age 13, and was less than 13 per 1,000 by age 22. No such cancer was found among 400 females exposed in utero during other trimesters than the first. No excess of other cancers or of other diseases was found among the 804 live-born females or 877 males.
