Diethylstilbestrol (DES)

The substance diethylstilbestrol (DES) is a synthetic, nonsteroidal estrogen, which was first made in 1938. Initially the substance was seen as a great scientific breakthrough, drawing on research that documented the importance of naturally occurring estrogen in women. Wide-scale use of DES by pregnant women to prevent miscarriage beginning in the 1940s ended in 1971 when researchers discovered that some daughters of women who took DES had developed a rare cancer, called clear-cell adenocarcinoma of the vagina. Researchers have since found that daughters of women who took DES face a higher risk of certain cancers and of structural abnormalities in the genital area. The example of DES, used by two to three million American women, has been used to dramatize the risk of improperly tested medicine during pregnancy.