Diethylstilbestrol (DES) is a synthetic form of the female hormone estrogen.It was prescribed to pregnant women between 1940 and 1971 to prevent miscarriage, premature labor, and related complications of pregnancy ().The use of DES declined after studies in the 1950s showed that it was not effective in preventing these problems.

: https://www.cancer.gov/about-cancer/causes-prevention/risk/hormones/des-fact-sheet