DES exposure refers to contact with diethylstilbestrol, a synthetic estrogen prescribed to pregnant women in the United States between 1940 and 1971. The drug was given to prevent miscarriage, premature labor, and other pregnancy complications, but it was later discovered to cause serious health problems in the mothers who took it, the children exposed in the womb, and potentially even grandchildren. An estimated 5 to 10 million Americans were exposed to DES, either directly or during fetal development.
In 1971, clinicians at Massachusetts General Hospital documented eight cases of a rare vaginal cancer in women under 20, all of whom had been exposed to DES before birth. The FDA quickly issued a warning to all U.S. doctors to stop prescribing DES to pregnant women. Since then, decades of follow-up research have revealed a wide range of health consequences that continue to affect exposed individuals today.
How DES Affects Exposed Daughters
Women who were exposed to DES in the womb, often called “DES daughters,” face the most well-documented health risks. The drug is classified as an endocrine-disrupting chemical, meaning it interfered with normal hormonal development during critical stages of fetal growth. This disruption left lasting changes in the reproductive tract that can affect health throughout life.
The most alarming risk is clear cell adenocarcinoma (CCA), a rare cancer of the vagina or cervix. Before DES, this cancer was virtually unheard of in young women. While the absolute risk remains relatively low, it is dramatically elevated compared to the general population, and cases have been diagnosed in DES daughters well into middle age and beyond.
Structural changes to the reproductive tract are far more common. In one study of 537 women with documented DES exposure, 33% had visible abnormalities of the cervix. Among those who underwent imaging, 57% had a T-shaped uterus with a small cavity, a distinctive malformation strongly linked to DES. Others showed constriction rings or unusually small uterine cavities. These structural differences directly affect the ability to carry a pregnancy.
Pregnancy Complications for DES Daughters
The reproductive consequences of DES exposure are striking. A major study published in the New England Journal of Medicine tracked cumulative risks in exposed women compared to unexposed women and found significantly higher rates across nearly every pregnancy outcome measured:
- Infertility: 33.3% of DES daughters vs. 15.5% of unexposed women
- Spontaneous abortion (miscarriage): 50.3% vs. 38.6%
- Preterm delivery: 53.3% vs. 17.8%, a nearly threefold difference
- Second-trimester pregnancy loss: 16.4% vs. 1.7%
- Ectopic pregnancy: 14.6% vs. 2.9%
- Preeclampsia: 26.4% vs. 13.7%
- Stillbirth: 8.9% vs. 2.6%
Women with abnormal uterine findings had even worse outcomes. Among those with structural changes visible on imaging, only 29% achieved a term pregnancy, compared to 50% of DES-exposed women whose imaging appeared normal. More than half of women with abnormal findings never carried a pregnancy to term.
Breast Cancer Risk for Mothers Who Took DES
The women who actually took DES during pregnancy also face increased health risks, particularly for breast cancer. Studies have found a modest but real association, with a relative risk of 1.27, meaning DES mothers were about 27% more likely to develop breast cancer than women who didn’t take the drug. This elevated risk held steady regardless of whether a woman had a family history of breast cancer or used oral contraceptives or hormone replacement therapy later in life. For women born before the mid-1940s who know or suspect they took DES, this is relevant information for ongoing cancer screening conversations.
Effects on DES Sons
Men exposed to DES in the womb have received less research attention than daughters, but known risks include undescended testicles (cryptorchidism), cysts on the structures near the testes, and possible effects on fertility. DES is an endocrine disruptor, and male reproductive development is highly sensitive to estrogen levels during fetal life. The research on cancer risk in DES sons has been less conclusive, with some studies suggesting slightly elevated overall cancer rates but no confirmed link to testicular or prostate cancer specifically.
What About Grandchildren?
One of the more concerning questions is whether DES effects carry into a third generation, the children of DES daughters and sons. Epigenetic changes, alterations in how genes are expressed without changing the DNA itself, could theoretically transmit some effects. A National Cancer Institute study tracking third-generation offspring found reassuring results overall: DES exposure was not associated with increased risk of overall cancer, breast cancer, or severe cervical abnormalities in granddaughters. No cases of clear cell adenocarcinoma were reported.
There was a suggestion of elevated borderline ovarian cancer risk in granddaughters, but the numbers were too small to draw firm conclusions. Among grandsons, overall cancer risk appeared slightly elevated but again with wide statistical uncertainty. The risk of testicular cancer was not elevated, and no cases of prostate cancer were reported. Research in this area is still maturing, but so far, third-generation effects appear limited compared to the direct impact on DES daughters and sons.
How to Find Out If You Were Exposed
No blood test, urine test, or other medical analysis can detect DES exposure. The only way to confirm it is through medical records or family history. If your mother was pregnant with you between 1940 and 1971, particularly if she had a history of miscarriage or pregnancy complications, DES exposure is worth investigating. The CDC developed a DES Self-Assessment Guide to help individuals evaluate their likelihood of exposure based on the circumstances of their mother’s pregnancy.
Old obstetric records, pharmacy records, or hospital files may contain documentation. Some women remember being told they took “pregnancy vitamins” or pills to prevent miscarriage. The drug was prescribed under dozens of brand names, which can make identification tricky. If your mother is still living, asking directly is the simplest starting point.
Screening Recommendations for DES Daughters
The American Society for Colposcopy and Cervical Pathology (ASCCP) recommends that DES-exposed women receive annual screening for clear cell adenocarcinoma using cervical and vaginal cytology until at least age 65. This screening is more thorough than a standard Pap test. It involves separate collections from the cervix and all four walls of the vagina, either sampled individually or circumferentially, with careful attention to the upper vagina and vaginal sidewalls where DES-related changes tend to occur.
After age 65, screening can be discontinued if the woman otherwise meets standard criteria for stopping cervical cancer screening. However, continuing annual screening beyond 65 is also considered acceptable after a conversation weighing the lack of strong evidence on effectiveness against the potential harms of screening in postmenopausal patients. Women who have had a hysterectomy with removal of the cervix, and who have no other indications for screening, can discontinue DES-specific screening.
Because DES daughters are now in their 50s through early 80s, many are aging out of the highest-risk window. But the screening recommendations remain in place, and awareness matters for those who may not have been screened appropriately throughout their lives.