DES daughters, or women who were exposed to the drug DES (diethylstilbestrol) while in their mother's womb, are at risk for an array of health problems. If your mother was treated with DES (which she may be familiar with as synthetic estrogen) between 1940 and 1971, particularly in the first five months of pregnancy, the drug may have affected the development of your reproductive organs. DES daughters are at a higher risk for miscarriage, preterm birth, ectopic pregnancy, and a rare form of cancer called clear cell adenocarcinoma.