Diethylstilbestrol (DES) is a medication once prescribed in the United States to prevent miscarriage or premature delivery. Doctors stopped prescribing DES after the discovery of medical problems in the children of women who had taken it while pregnant – known as DES sons and DES daughters.
Sons born to women who took DES while pregnant have a slightly higher risk of abnormalities of the scrotum and decreased sperm counts. They also experience an increased risk for non-cancerous epididymal cysts and auto-immune disorders.
Diethylstilbestrol can also cause feminization of the male fetus. In some cases DES sons have only one testis, or both remain in the abdominal cavity. Some evidence suggests that DES sons have a increased prevalence of hypospadias.
Female offspring, too, can have effects from DES taken by their pregnant mothers. Additionally, mothers who took DES while pregnant have a modestly increased risk for breast cancer. It is important for men and women of all ages, regardless of their intention to reproduce, to inquire about their own possible history of exposure to DES in utero.
Between 1941 and 1971, an estimated 5 million to 10 million Americans were exposed to DES , including women who took the drug during pregnancy and their children.
More than 30 years of research have confirmed that DES is a teratogen, an agent that can cause malformations of an embryo or fetus. However, not all exposed persons will experience DES-related health problems. Current research is examining possible inherited effects of DES in third-generation offspring – that is, grandchildren of the women who took DES. Some evidence suggests the effects skip a generation. Researchers are also following the health of DES-exposed adults to determine whether other problems develop with age.
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From the 1940s until the late 1980s, DES tablets were FDA-approved as estrogen-replacement therapy for conditions such as abnormal ovarian development, premature ovarian failure, post-oophorectomy (surgical removal of ovaries), atrophic vaginitis (thinning of the vaginal lining), and to suppress postpartum lactation for the prevention of breast engorgement. Until penicillin was available, DES was also used to treat gonorrheal vaginitis.
Doctors first prescribed DES for off-label use – meaning for a condition other than original one for which the medicine was developed – in the 1940s to women with histories of miscarriage. Eventually, the FDA approved DES for prevention of miscarriage. Scientists and physicians initially thought DES to be both effective and safe for the pregnant woman and her developing baby. Then, six years following the Federal Drug Administration’s (FDA) approval of DES, a double-blind study of pregnant women found that pregnant women taking DES had just as many miscarriages and premature deliveries as women who did not take DES, yet doctors continued routinely prescribing the drug. By the late 1960s, most leading obstetrical textbooks said DES was ineffective at preventing miscarriage.
By the 1990s, the only approved use of DES were for treatment of advanced prostate cancer in men and treatment of advanced breast cancer in postmenopausal women.
In November 1971, the FDA advised all U.S. physicians to stop prescribing DES to pregnant women due to the discovery of links to a rare vaginal cancer in DES offspring. The drug was not actually banned, however, and doctors continued to prescribe DES well beyond 1971. The last remaining American manufacturer of DES, Eli Lilly, stopped making and marketing DES in 1997.