DES: 40 Years of Research With More to Learn

Taken from the March/April 2012 issue of The Women's Health Activist Newsletter.

Diethylstilbestrol (DES) is a synthetic estrogen that was given as an anti-miscarriage drug to millions of pregnant women primarily between 1938-1971 (but not limited to those years).Unfortunately, DES not only did not work to prevent miscarriage, but also caused severe medical problems for both the women who took the drug and their children who were exposed to the drug in utero, who are known as DES Daughters and DES Sons.ii In 1971, the Food and Drug Administration (FDA) advised providers not to prescribe DES to pregnant women when it was found to increase the risk of clear-cell adenocarcinoma, a rare vaginal cancer, among DES Daughters.

DES is now known to cause a 30 percent increased risk of breast cancer among women who took the drug. DES Sons are at an increased risk for non-cancerous growths on the testicles called “epididymal cysts.” It is not yet clear if DES increases the risks for other health problems in DES Sons, and studies are on-going.iii

A recent article in The New England Journal of Medicine provides the most comprehensive look to-date at health issues experienced by DES Daughters and paints a devastating picture of the tragedy caused by prenatal exposure to DES.iv According to lead author Robert N. Hoover, M.D., Sc.D., of the National Cancer Institute DES Follow-up Study, researchers can say conclusively that in utero DES exposure is linked to 12 adverse health problems for DES Daughters (see chart).v “It isn’t as if we didn’t have confirming information previously, because we did, but it had never been collected in one article in a respected publication,” says DES Action USA’s Program Director Kari Christianson. “Look at what this drug has done. What other prescription drug has had this much negative impact over the lives and health of women?”

Risks for DES- Daughters compared to non-exposed women 
Outcome DES Daughters’ Increased Risk
Clear-cell adenocarcinoma (CCA) vagina or cervix 40 times higher
Neonatal death 8 times higher
Pre-term delivery 4.7 times higher
Loss of second-trimester pregnancy 3.8 times higher
Ectopic pregnancy 3.7 times higher
Stillbirth 2.4 times higher
Infertility 2.4 times higher
Early menopause (before age 45) 2.4 times higher
Cervical intraepithelial neoplasia (CIN2+) 2.3 times higher
Breast cancer (age 40 and higher) 1.8 times higher
First trimester miscarriage 1.6 times higher
Preeclampsia 1.4 times higher

Source: National Institute of Health/National Cancer Institute

Assessing Your Health History

You cannot look at an individual and tell she or he was exposed to DES before birth. Unlike Thalidomide (which was prescribed in the 1950s to treat morning sickness), where the damage is external, DES Sons and Daughters were harmed internally: primarily with respect to the reproductive systems. Many DES Daughters, but not all, have a T-shaped uterus and other reproductive tract abnormalities.

Medical record confirmation of exposure going back to when DES was the standard of care for problem pregnancies is nearly impossible to obtain now. Anyone who suspects DES exposure should research their health history. Did your mother have a previous miscarriage or was she prescribed medication while pregnant with you? Are the health problems you’ve experienced through your life consistent with what is now linked to DES? Even prenatal vitamins are suspect because, back in the 1950s, their formulations sometimes included DES. Putting puzzle pieces together can help provide an answer.

DES Daughters are urged to consider their exposure as part of their medical According to DES Action’s Christianson: “They and their health care providers should pay attention to the particular screening guidelines for DES Daughters. That includes a special Pap/pelvic exam every year to check for CCA, because DES Daughters are considered at life-long risk. They’ll also want to be vigilant about breast screenings, as DES Daughters are about two times more likely to develop breast cancer after age 40 than unexposed women.” Finally, it is important that DES Daughters receive high-risk obstetric care during pregnancy.

Sadly, the DES story is still unfolding. While the NEJM article outlines what is known so far, there remains a nagging concern that additional health problems may emerge as DES Daughters mature past menopause. Those who were able to have children worry what the future holds for their children, who are DES Grandchildren. Research studies and anecdotal reports raise the possibility that DES exposure’s negative impacts, such as infertility, may extend into future generations. National Cancer Institute (NCI) researchers are actively studying generational impacts while continuing to follow the health of DES Daughters and Sons. “Continuing these research studies is vital to help millions of individuals who need information to protect their health. The DES community is desperate for answers,” Christianson says.

As an endocrine-disrupting compound, DES is one of a number of substances that interfere with hormone functions. Another, Bisphenol A (BPA), is currently under scrutiny for safety concerns, especially when exposure occurs during fetal development.vii BPA is found in many household plastics such as food storage containers, baby bottles, and the lining of cans of food, along with cash register receipts and even dental sealants.viii Most of the health issues raised about BPA sound familiar: cancers and reproductive system problems.ix  Those health concerns shouldn’t be a surprise, given that both DES and BPA are synthetic estrogens with very similar chemical structures.

Researchers have valid scientific evidence regarding adverse health effects caused by DES. “We don’t have to wonder. We know the endocrine disrupting chemical DES hurt us. We are the poster population for the dangers of environmental estrogens like drugs and chemicals. It is past time to get serious about government regulation of endocrine disruptors, so tragedies like DES don’t happen again,” warns Christianson.

History in the Making

DES history was made in January 2012 at the Federal Courthouse in Boston when U.S. Magistrate Judge Marianne Bowler ordered drug makers to negotiate settlements with 53 DES Daughters who filed suit claiming their breast cancers were linked to prenatal DES exposure. The suit maintained that DES Daughters were nearly two times more likely to develop breast cancer after age 40 than unexposed women, and that the risk increases with age. Drug company lawyers had pressed to have the suit dismissed, but Judge Bowler rejected their request. Although the drug companies had agreed to mediate damage awards if the judge did not throw out the case, they are now re-considering their options and may appeal. This is the first major DES breast cancer lawsuit — although other successful DES product liability litigation has provided settlements for those who have experienced vaginal and cervical cancers, infertility, and other DES-related health issues. To learn more about this issue and the lawsuit, see

Fran Howell is Executive Director of DES Action USA

The continued availability of external resources is outside of the NWHN’s control. If the link you are looking for is broken, contact us at to request more current citation information.


[i] Centers for Disease Control and Prevention Website. “CDC’s DES Update.” No date. Retrieved December 19, 2011 from

[ii] Dieckmann WJ, Davis ME, Rynkiewicz LM et al. “Does the administration of diethylstilbestrol during pregnancy have therapeutic value?” American Journal of Obstetrics and Gynecology 1953; 66(5):1062-1081.

[iii] Centers for Disease Control and Prevention Website. “CDC’s DES Update: Known Health Effects for DES Sons”, No date. Retrieved January 23, 2012 from

[iv] Hoover RN, Hyer M, Pfeiffer RM, et al. “Adverse Health Outcomes in Women Exposed In Utero to Diethylstilbestrol”, New England Journal of Medicine 2011; 365:1304-1314.

[v] National Cancer Institute Website, “DES Follow-up Study.” No date. Retrieved December 19, 2011 from

[vi] Centers for Disease Control and Prevention Website. “CDC’s DES Update.” No date. Retrieved December 19, 2011 from

[vii] Environmental Protection Agency Website. “Bisphenol A (BPA) Action Plan Summary.” No date. Retrieved December 19, 2011 from

[viii] National Institute of Environmental Health Studies Website. ”Bishpenol A (BPA):  Expanding Research to Impact Human Health.  No date.  Retrieved December 19, 2011 from

[ix] The Endocrine Disruptor Exchange Website.  “Critical Windows of Development.”  No date.  Retrieved on December 19, 2011 from