DES exposure was historically used to prevent:
Diethylstilbestrol history illustrates misuse of synthetic hormone in obstetrics. Between 1940s and early 1970s physicians prescribed DES believing synthetic estrogen would support pregnancy by stimulating placental growth, increasing uterine blood flow and preventing miscarriages especially in women with recurrent abortion history. Randomized trials later showed no preventive benefit and revealed teratogenic sequelae in offspring. Marketed for threatened abortion prophylaxis, DES was not intended for neural tube defects or infection treatment. Its extensive use to prevent miscarriages despite lack of efficacy became notorious example of iatrogenic endocrine disruption causing reproductive tract anomalies and neoplasia.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 20: DES historically used to prevent miscarriages.