Diethylstilbestrol (DES)

Health risks of Diethylstilbestrol (DES)

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 daughters and DES sons.

DES daughters have a slightly higher risk of developing:

  • Abnormal cervical cells that cause an abnormal Pap test
  • Cancer of the cervix or vagina
  • Structural problems in reproductive organs, such as a T-shaped uterus or a weakened cervix, which can cause infertility and a higher risk of preterm labor

Additionally, women who took DES when pregnant have a modestly increased risk for breast cancer. One study showed a 2.5-fold increase in breast cancer after age 40 for DES daughters.

DES sons also face slightly higher health risks. It is important for men and women of all ages, regardless of intention to reproduce, to explore their own history of possible exposure to DES in utero (in the womb).

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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DES History

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 was 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.