Millions of women alive today were exposed to a chemical called DES – diethylstilbestrol – in their mother’s uterus. The chemical, an early synthetic estrogen, was administered to some pregnant women before 1971 to help reduce risk of miscarriages and prematurity.

Only later did doctors discover that it a) didn’t help with these complications and b) it heightened certain health risks to female babies exposed to the chemical.

My mother was given DES (though I only found out when I was in my 30s), so I’m one of those DES daughters and have reason to be interested in a new report in the New England Journal of Medicine that takes a thorough look at the heightened medical risks.

The scientists, from a slew of institutions including the National Institutes of Health, examined data from three studies started in the 1970s, encompassing 4,653 women exposed to DES as fetuses and 1,927 similar women who weren’t exposed. The amount of the chemical the women were exposed to varied from case to case; the scientists found that women whose vaginal tissue samples showed more signs of abnormality (an indication of higher and earlier exposure to the hormone) were more likely to experience these adverse events.


There’s quite a list of them, with various levels of heightened risk – the ones to do with reproduction were tracked till age 45 and the others up to age 55.

The first abnormality to be unearthed was a rare kind of vaginal cancer called clear cell carcinoma — doctors first identified that in the 1960s.

Of the other 11, ones linked to reproductive issues were: infertility; spontaneous abortion; preterm delivery; loss of second-trimester pregnancy; ectopic pregnancy; preeclampsia, stillbirth and neonatal death.

The remaining three were early menopause; grade 2 or higher intraepithelial neoplasia (an abnormal growth on the cervix); invasive breast cancer at 40 years of age or older.


The amount of heightened risk varied. On the low end, DES daughters were 1.4 times more likely to experience preeclampsia (high blood pressure associated with pregnancy). On the higher end, the risk for preterm delivery was 4.68 times higher and the risk for neonatal death -- the largest difference on the list -- was more than eight times higher. Breast cancer risk was almost doubled (1.82 times more likely).

This is annoying, but it’s good to remind oneself that just because risks are raised doesn’t mean one is doomed to experience the various complications. If the absolute risk is low, double the absolute risk is still low as well. For example, though the breast cancer risk was nearly doubled, the measured risk was about 4% versus about 2%.

Ironically, by the time I was exposed to DES, four clinical trials had already shown it didn’t help prevent miscarriages, but it was prescribed for my mother anyway.