Pregnancy Drug DES, What You Should Know

Pregnancy Drug DES

More than half a century ago, millions of women were prescribed the pregnancy drug DES (diethylstilbestrol), and although it was eventually removed from the market for that purpose, its ghosts are still among us. A case in point is the recent trial in which four sisters with breast cancer sued one of the drug makers (Eli Lilly) because they said their cancer was caused by the DES their mother took while pregnant.

What should you know about DES?

DES is a synthetic type of estrogen that was prescribed to 5 to 10 million pregnant women between 1938 and 1971, according to the Centers for Disease Control and Prevention (CDC) for the purpose of preventing premature labor, miscarriages, and pregnancy complications. It was eventually found not to be effective for these purposes.

Although DES was no longer prescribed for pregnant women after 1971, some of the daughters and sons of those women appear to have been affected by the drug, and the impact may continue on for more generations. Here’s what researchers and other experts have to say about what is known—and uncertain—about DES.

DES and daughters of DES mothers
It’s been shown that DES interferes with the endocrine system. As an endocrine-disrupting substance, DES can cause birth defects, cancer, and other developmental problems. DES is most destructive when exposure occurs during development of a fetus (in utero).


A large study conducted by the National Cancer Institute and published in 2011 used data from three studies and followed them up long-term. The data were from 4,653 women exposed in utero to DES and 1,927 who were not exposed.

Overall, the researchers found that women exposed to DES (first figure) as compared to those not exposed (second figure) were at increased risk for the following problems:

  • Preterm delivery: 53.3% vs 17.8%
  • Spontaneous abortion: 50.3% vs 38.6%
  • Infertility: 33.3% vs 15.5%
  • Preeclampsia: 26.4% vs 13.7%
  • Ectopic pregnancy: 14.6% vs 2.9%
  • Stillbirth: 8.9% vs 2.6%
  • Grade 2 or higher cervical intraepithelial neoplasia: 6.9% vs 3.4%
  • Early menopause: 5.1% vs 1.7%
  • Breast cancer at age 40 or older: 3.9% vs. 2.2%

More information about DES

  • DES increases lower genital tract cancer risk. Daughters of women who took DES while pregnant are at about 40 greater risk of developing a rare cancer called clear cell adenocarcinoma of the lower genital tract than women who were not exposed. Approximately 1 in 1,000 exposed daughters develops this cancer.
  • Drugs similar to DES could have the same effects. The Journal of the American Medical Association published a list of these drugs, along with the most commonly used spellings for DES, in 1976. That list can be seen here.
  • DES cannot be detected. No blood, urine, or skin test is available that can detect exposure to DES. The CDC has an interactive Self-Assessment Guide plus other information about what you can do about possible exposure to DES on its DES website.
  • DES exposure also can affect men. For example, a Boston University study found that prenatal exposure to DES increases the risk of urogenital problems (e.g., cryptorchidism [undescended testes], epididymal cysts, and testicular inflammation or infection) in men whose mothers used the drug, especially if they took it during early pregnancy.
  • DES may be beneficial for prostate cancer. One of the first hormone treatments used for prostate cancer was DES, and it is still used. A recent study conducted in the United Kingdom reported that DES used in elderly men with hormone-resistant prostate cancer resulted in several benefits, including a slowing in the rise of prostate-specific antigen (PSA) and pain relief.

Bottom line
Although DES no longer is prescribed for pregnant women, it has lasting effects that may span generations. Men and women (especially if they are pregnant) who believe they were exposed to the pregnancy drug DES should discuss this possibility with their healthcare providers.

Centers for Disease Control and Prevention
Hoover RN et al. Adverse health outcomes in women exposed in utero to diethylstilbestrol. New England Journal of Medicine 2011 Oct 5; 365(14): 1304-14
National Cancer Institute
Palmer JR et al. Urogenital abnormalities in men exposed to diethylstilbestrol in utero: a cohort study. Environmental Health 2009 Aug 18; 8:37
Wilkins A et al. Diethylstilbestrol in castration-resistant prostate cancer. BJU International 2012 Oct 30

Image: Morguefile