Dangerous Exposures to Unborn Children

In utero diethylstilbestrol exposure results in increased cancer risks

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Starting in 1940, it was common for women to be prescribed diethylstilbestrol (DES), a synthetic form of estrogen, to prevent complications during pregnancy. Today, that exposure may be haunting the daughters of women who took the drug.

Women whose mothers took DES during pregnancy are at substantially greater risk of developing infertility problems and cancer, including breast cancer. A large study conducted by the National Institutes of Health (NIH) has indentified a link between in utero (in the womb) exposure to DES and a host of health risks.

"Ask your mother if she took DES during her pregnancy with you."

For more than three decades, DES was given to women to prevent various problems during pregnancy. It was found to be ineffective in the 1950s. In the 1960s, daughters who were exposed to the drug began having a rare type of cancer of the vagina known as clear cell adenocarcinoma (CCA). The DES link was eventually identified.

Finally in 1971,  the U.S. Food and Drug Administration (FDA) alert physicians not to prescribe the drug to pregnant women. But by then, between 5-10 million women and their babies had been exposed to DES, a drug manufactured under a variety of product names and available in pills, creams and vaginal suppositories.

For this study, more than 6,500 women - 4,600 of whom had been exposed to DES - were followed, starting in 1992.

Researchers found women whose mothers had taken the drug were at an increased risk of 12 medical conditions. Among the most prominent were a twofold increased risk of infertility and a fivefold greater risk of having pre-term deliveries as compared to women who were not exposed to the drug.

In terms of cancer, the study found:

  • DES-exposed daughters had an 80 percent higher risk of developing breast cancer after the age 40.
  • By age 55, one in 25 DES-exposed women will have cellular changes in cervix or vagina; and one in 50 will develop breast cancer.
  • They have a significantly greater risk of rare vaginal cancer, CCA
  • This risk continues through age 40.
  • They have a twofold increased risk of pre-cancerous cells in cervix or vagina.

While DES-exposed sons were not included in this study, previous research has found testicular abnormalities.

The study will continue and researchers will look at the possible health impact on grandchildren of women who took DES, as genetic changes could have been caused by the drug and passed down.

This study was published in the October 6, 2011 issue of the New England Journal of Medicine.

Reviewed by: 
Review Date: 
October 6, 2011
Last Updated:
October 6, 2011