Diethylstilbestrol, commonly called DES, is a synthetic form of estrogen first produced in 1938. It was prescribed to millions of pregnant women from the mid-1940s through the early 1970s to prevent miscarriage. In 1971, it was linked to a rare vaginal cancer in the daughters of women who took it, and the FDA pulled it from use in pregnancy. Today it is classified as a known human carcinogen, and its health effects continue to ripple through multiple generations.
How DES Works in the Body
DES was the first estrogen available in pill form. Although it is not chemically identical to the estrogen your body makes naturally, it binds tightly to the same estrogen receptors on cells, particularly in reproductive tissues like the uterus, cervix, vagina, and pituitary gland. Once bound, DES and its breakdown products enter the cell nucleus and stimulate cell growth. This made it a potent driver of tissue development, which is exactly why it caused problems when a fetus was exposed during critical windows of organ formation.
The damage from DES appears to be tissue-specific. Lesions and abnormalities show up predominantly in organs that are naturally responsive to estrogen, suggesting the estrogen receptor itself acts as a homing signal, concentrating DES in the tissues most vulnerable to its effects.
Why It Was Prescribed and When It Stopped
Doctors began prescribing DES in the mid-1940s to women considered at risk of miscarriage. The logic seemed straightforward: estrogen supports pregnancy, so supplementing it should help women carry to term. By the early 1950s, a clinical trial at the University of Chicago (the Dieckmann Study) enrolled pregnant women to test whether DES actually worked for this purpose. It did not show clear benefits, yet prescriptions continued for roughly two more decades.
The turning point came in 1971, when researchers identified a connection between mothers who had taken DES during pregnancy and cases of a rare vaginal cancer in their daughters. The FDA acted quickly, notifying healthcare providers across the country that DES should no longer be prescribed to pregnant women. By that time, millions of women had already taken it, and their children had already been exposed in the womb.
DES also had non-medical uses. Until the 1970s, it was mixed into animal feed or implanted as pellets under the skin of cattle and chickens to accelerate growth. Concerns about trace amounts of the hormone in meat led to bans on this practice as well.
Health Risks for DES Daughters
Women who were exposed to DES before birth, often called “DES daughters,” face a distinct set of health risks. The most alarming is clear cell adenocarcinoma, a rare cancer of the vagina or cervix. DES daughters have roughly 40 times the risk of developing this cancer compared to unexposed women. The first cases were diagnosed in very young women, some still teenagers. Later research showed the elevated risk persisted as these women aged into their 40s and 50s, though the cancer remained rare overall, affecting approximately 1 in 1,000 DES daughters.
Beyond cancer, many DES daughters developed structural changes to their reproductive organs. A T-shaped uterus is one of the most recognized abnormalities, along with a hooded cervix, cervical growths called cockscombs, and pseudopolyps. These changes can affect fertility and increase the risk of pregnancy complications such as preterm birth.
Health Risks for DES Sons
Men exposed to DES in utero have received less research attention, but they are not unaffected. The CDC advises men born between 1938 and 1971 who may have been exposed to contact a healthcare provider if they notice lumps in their testicles. Reproductive abnormalities, including undescended testicles and cysts along the reproductive tract, have been reported in this group.
Effects on the Third Generation
One of the more unsettling aspects of DES is that its effects did not stop with the children who were directly exposed. Research on grandchildren of women who took DES has found that the drug alters the epigenome, the chemical markers that control how genes are turned on and off, in ways that persist across generations. DES disrupts the epigenetic reprogramming of fetal eggs and sperm, meaning changes can be passed down even though the grandchildren were never directly exposed to the drug.
In practical terms, studies have found that grandchildren born through the maternal line (children of DES daughters) have slightly elevated rates of preterm birth and low birth weight. In one multigenerational study, the preterm birth rate was 14.8% among children of DES-exposed daughters, compared to 7.7% among children of daughters born before their mothers received DES. Interestingly, children of DES-exposed sons did not show the same increase in preterm birth, suggesting the effects transmit more strongly through eggs than through sperm.
Screening for Exposed Individuals
If you were born between 1938 and 1971 and your mother may have taken DES during pregnancy, specific screening steps are recommended. For women, this means regular gynecological exams that include a Pap test, pelvic exam, clinical breast exam, and mammograms at the recommended intervals. For men, self-examination for testicular lumps is important.
Women who were pregnant during that period and may have been prescribed DES should also stay current with mammograms and breast exams, and report any breast lumps promptly. The CDC specifically encourages these women to discuss their DES use with their children, since many people exposed in utero do not know about it. Medical records from that era are often unavailable, so a conversation with a parent or relative may be the only way to find out.
Where DES Stands Today
DES is no longer prescribed during pregnancy and is banned as a livestock growth stimulant. It was once used to treat advanced prostate cancer, but that application has largely been abandoned because of its side effects. For all practical purposes, DES is a drug of the past, though its consequences are very much in the present. The NCI continues a long-running follow-up study tracking health outcomes in exposed individuals, and the emerging data on third-generation effects means researchers are still learning the full scope of what this drug did.