Diethylstilbestrol (DES) is a powerful synthetic estrogen that was prescribed to pregnant women between 1946 and 1977. Doctors believed it could prevent miscarriages and treat bleeding during pregnancy. However, research later showed that DES caused serious health problems — not just for the women who took it, but for their children and even grandchildren. If you or a family member may have been exposed, understanding the risks is an important first step.
What Is Diethylstilbestrol?
Diethylstilbestrol, often called DES, was the first synthetic estrogen ever produced. It was widely prescribed across North America and Europe for more than three decades. In Canada, as in many other countries, it was given to pregnant women who were considered at risk of losing their pregnancy.
DES was sold under several brand names, including Distilbene and Stilboestrol. It was available in pill, injection, and suppository forms. For years, it was considered a medical breakthrough. Unfortunately, that view changed dramatically once researchers began studying the children born to mothers who had taken it.
By 1971, the U.S. Food and Drug Administration flagged a clear link between DES and a rare vaginal cancer in young women. Canada followed with its own restrictions, and by 1977, DES was no longer prescribed to pregnant women in most Western countries. However, the health consequences of this drug continued to unfold for decades afterward.
How Diethylstilbestrol Was Used During Pregnancy
When DES first came onto the market, the medical community was optimistic. Miscarriage was a poorly understood and emotionally devastating experience. Doctors were eager to offer a solution, and DES seemed promising at the time.
Women were often prescribed DES starting in the first trimester of pregnancy. Some took it for only a few weeks, while others continued throughout their entire pregnancy. The dose and duration varied widely between patients.
Ironically, later studies showed that DES did not actually prevent miscarriage at all. A landmark clinical trial in the 1950s had already suggested it was ineffective, but the drug remained in widespread use for years after. As a result, millions of women and their unborn children were exposed to a drug that offered no benefit — and carried serious risks.
Health Risks for DES-Exposed Daughters
The children of women who took diethylstilbestrol during pregnancy — often called “DES daughters” — face a unique set of health challenges. These risks became most apparent between the 1990s and 2010s, when many DES daughters reached their reproductive years and beyond.
Reproductive and Structural Abnormalities
DES daughters are at higher risk of abnormalities affecting the cervix and uterus. These structural differences can make it harder to carry a pregnancy to term. In some cases, they can lead to infertility.
Furthermore, DES daughters who do become pregnant face a significantly higher risk of complications. These include miscarriage, ectopic pregnancy (where the fertilized egg implants outside the uterus), and premature birth. If you are a DES daughter and are planning a pregnancy, it is essential to share this history with your healthcare provider.
Increased Cancer Risk
One of the most serious risks linked to DES exposure is a rare form of cancer called clear cell adenocarcinoma of the vagina and cervix. This cancer is uncommon in the general population but is found at significantly higher rates in DES daughters. The Canadian Cancer Society recognizes DES exposure as a known risk factor for this type of cancer.
In addition, research suggests that DES daughters may also have a modestly higher risk of breast cancer as they get older. Regular screening is therefore especially important for this group. Talk to your family doctor about what screening schedule is right for you.
Other Gynaecological Concerns
Beyond cancer, DES daughters may experience a range of gynaecological issues throughout their lives. These can include irregular Pap test results, benign growths, and changes in cervical tissue. Many of these conditions are manageable when caught early through regular check-ups.
For this reason, DES daughters are encouraged to have more frequent gynaecological exams than the general population. Your provincial health plan covers many of these routine screenings. Ask your family doctor or gynaecologist about the right monitoring plan for your situation.
Health Risks for DES-Exposed Sons
While much of the research has focused on DES daughters, male children exposed to diethylstilbestrol in the womb also face some health risks. However, these effects are generally considered less severe than those seen in females.
DES sons may have a higher risk of certain genital and urinary tract abnormalities. These include conditions such as hypospadias, where the opening of the urethra is not in the typical position. Undescended testicles and cysts in the epididymis (a structure near the testicle) have also been reported more frequently in this group.
Some studies have suggested a possible link between DES exposure and testicular cancer, though the evidence is less definitive than for vaginal cancer in women. Health Canada continues to monitor research on DES and its long-term effects on all exposed individuals.
What About the Third Generation? DES Grandchildren
One of the most surprising and concerning findings in DES research involves the third generation — the grandchildren of women who took the drug. Scientists have been investigating whether the effects of DES can be passed down through generations, a concept known as transgenerational epigenetic inheritance.
Some early research suggests that DES granddaughters may have a slightly elevated risk of certain cancers and reproductive issues. Similarly, DES grandsons may have a higher rate of certain genital abnormalities. However, this area of research is still evolving, and experts caution that more studies are needed before firm conclusions can be drawn.
If your mother is a DES daughter, it may be worth discussing this family history with your doctor. Being aware of your background allows your healthcare team to monitor your health more closely and catch any concerns early.
DES Exposure in Canada: What You Need to Know
It is estimated that millions of women across North America received DES prescriptions between 1946 and 1977. In Canada, thousands of women and their children were affected. Because DES was prescribed so broadly, many Canadians may not know they were exposed.
If you were born between approximately 1947 and 1978, and your mother experienced any complications during her pregnancy, it is worth asking whether she may have been prescribed DES. Old medical records, where available, can sometimes confirm this. Many hospitals and provincial health authorities have policies in place to help patients access older medical records.
For those who already know they are DES-exposed, the good news is that Canada’s healthcare system offers strong support. Your family doctor can help coordinate the appropriate specialists and screening programmes. Provincial health plans generally cover gynaecological exams, cancer screening, and specialist referrals when there is a documented medical reason.
According to Mayo Clinic’s overview of DES exposure, ongoing surveillance and early detection remain the most effective tools for managing the long-term risks associated with this drug.
When to See a Doctor
If you believe you or your child may have been exposed to diethylstilbestrol, do not wait for symptoms to appear before seeking medical advice. Many of the complications associated with DES, including structural abnormalities and early cancers, can be detected before they cause obvious problems.
Your first call should be to your family doctor. If you do not currently have a family doctor, a walk-in clinic can help in the short term and may be able to refer you to a gynaecologist or other specialist. Most provincial health plans will cover the necessary assessments once a potential DES exposure is identified.
You should seek medical attention promptly if you notice any of the following:
Unusual vaginal bleeding or discharge
Pelvic pain that is new or worsening
Difficulty becoming pregnant or repeated pregnancy losses
Abnormal results on a Pap test or cervical exam
Any lump or swelling in the pelvic or genital area
Remember, early detection makes a significant difference in outcomes. Do not hesitate to advocate for yourself or your child within the healthcare system.
Frequently Asked Questions About Diethylstilbestrol
What is diethylstilbestrol used for today?
Diethylstilbestrol is no longer prescribed to pregnant women anywhere in Canada or most of the world. Today, DES has very limited medical applications and is occasionally used in some countries to treat certain hormone-sensitive cancers, but only under strict medical supervision. Its use during pregnancy was banned in Canada after 1977 due to serious health risks to children.
How do I know if I was exposed to DES before birth?
The best way to find out is to ask your mother whether she was prescribed any medication to prevent miscarriage during her pregnancy with you. If she was pregnant between 1946 and 1977 and experienced any pregnancy complications, there is a chance she may have received diethylstilbestrol. Old medical records from your birth hospital may also confirm this, and your family doctor can help you request them.
What cancers are linked to DES exposure?
The most clearly established cancer risk from diethylstilbestrol exposure is clear cell adenocarcinoma of the vagina and cervix, a rare cancer that appears at much higher rates in DES daughters. There is also evidence suggesting a modestly elevated risk of breast cancer in DES daughters as they age. DES sons may have a slightly higher risk of testicular cancer, though research in this area is still ongoing.
Can DES affect my fertility?
Yes, diethylstilbestrol exposure before birth can affect fertility in women. DES daughters are more likely to have structural differences in the uterus and cervix that can make it harder to conceive or carry a pregnancy to term. They also face higher risks of ectopic pregnancy, miscarriage, and premature birth. If you are a DES daughter and are trying to conceive, speak to your doctor as early as possible so your pregnancy can be closely monitored.
Are DES grandchildren at risk of health problems?
Research into the health effects of diethylstilbestrol on grandchildren — the third generation — is still in early stages. Some studies suggest that DES granddaughters may have a slightly higher risk of certain cancers and reproductive issues, and DES grandsons may show a higher rate of genital abnormalities. If your mother is a DES daughter, it is worth mentioning this family history to your doctor so they can advise on any appropriate monitoring.
Is DES screening covered by provincial health plans in Canada?
In most provinces, routine gynaecological screenings such as Pap tests, pelvic exams, and specialist referrals are covered under provincial health plans when there is a documented medical reason — including a known history of diethylstilbestrol exposure. Coverage details vary by province, so it is best to speak with your family doctor or contact your provincial health authority to confirm what is included under your plan.
Key Takeaways
Diethylstilbestrol (DES) was a synthetic estrogen prescribed to pregnant women from 1946 to 1977 to prevent miscarriage — but it did not work, and it caused serious harm.
DES daughters face higher risks of uterine and cervical abnormalities, infertility, miscarriage, ectopic pregnancy, premature birth, and a rare vaginal cancer.
DES sons may experience urinary and genital tract abnormalities, though their risks are generally less severe than those seen in daughters.
Research is ongoing into the third-generation effects of DES on grandchildren, with some early evidence of elevated health risks.
If you were born between 1947 and 1978 and your mother had pregnancy complications, ask whether she may have been prescribed DES.
Speak to your family doctor or visit a walk-in clinic to discuss screening, monitoring, and referral options covered under your provincial health plan.
Early detection and regular medical follow-up are your best tools for managing the long-term risks associated with DES exposure.
Disclaimer: This article is for general informational purposes only and does not replace professional medical advice. Always speak with a qualified healthcare provider — such as your family doctor or a specialist — about your personal health situation and any concerns related to DES exposure.
