Diethylstilbestrol is a synthetic nonsteroidal estrogen. Human exposure to DES occurres through diverse sources, such as dietary ingestion from supplemented cattle feed and medical treatment for certain conditions, including breast and prostate cancers. From about 1940 to 1970, DES was given to pregnant women under the mistaken belief it would reduce the risk of pregnancy complications and losses however in 1971, DES was shown to cause a rare vaginal tumor in girls and young women who had been exposed to this drug in-utero.