DES or diethylstilbestrol dīˌĕthˌəlstĭlbĕsˈtrôl [key], synthetic nonsteroid female sex hormone having the same physiological effects as estrogen. In the 1940s and 50s DES was mistakenly believed to reduce the risk of miscarriage and was routinely prescribed for pregnant women believed to be at risk. In fact, it was later found to increase the risk of miscarriage and was then tested in a “morning-after” pill, a contraceptive pill that is taken after intercourse. In the late 1960s and early 70s a group of Boston physicians found that women whose mothers had taken DES during pregnancy had an unusually high rate of vaginal cancer, and it has since been implicated in various reproductive disorders and other conditions in female and male children of such mothers. The use of DES to prevent miscarriage was banned in 1973; its use as a growth accelerator in beef cattle was banned in 1979. It currently finds some use in the hormone treatment of certain types of cancer.

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