Prenatal diethylstilbestrol exposure and human genital tract abnormalities.

The incidence of clear cell adenocarcinoma of the vagina and cervix associated with intrauterine exposure to DES and similar compounds during the first half of pregnancy has increased. Ninety percent of these cancers have occurred in patients 14 years of age or older. Although these carcinomas are exceedingly rare, nonneoplastic abnormalities including vaginal adenosis, cervical eversion (ectropion), and transverse cervical and vaginal ridges are frequent in the exposed population, particularly if the drug was administered early in pregnancy. Current evidence favors a disturbance in development of the müllerian duct as the explanation of these changes. Whether DES is only a teratogen or also a carcinogen is unknown, as is the possible role of other factors in the development of cancer. An increased incidence of cancer among exposed males has not been documented.