Pregnancy Drug Linked to Breast Cancer

(Ivanhoe Newswire) -- Did your mother take a drug to avoid a miscarriage while she was pregnant with you?

That's something women should know, because new research suggests women born to mothers who took the synthetic estrogen known as diethylstilbestrol (DES) while they were pregnant are significantly more likely to develop breast cancer as they get older.

The federally funded study was based on an ongoing analysis of people whose mothers took DES during their pregnancies. This arm of the study looked at about 4,800 women who were exposed to DES in the womb, comparing breast cancer rates in them with those found in around 2,000 similar women who weren't exposed to DES. Results showed DES daughters older than 40 were nearly two-times more likely to develop breast cancer. DES daughters older than 50 may be at even higher risk, but the authors of the study say a longer follow up will be needed to say that for sure.

DES was widely used to prevent miscarriage between 1938 and 1971, when research first linked the drug to rare cancers of the vagina and cervix. The drug was banned from use by the Food and Drug Administration following that discovery.

Because many women exposed to DES are just now getting to the age where breast cancer is more common, researchers believe more DES-related cancers may be found. "This is unwelcome news for the 1 to 2 million women who were prenatally exposed to DES," write the authors, "and underscores the need for regular screening for breast tumors."

They also suggest DES daughters may want to say no to hormone therapy as well, as that treatment has already been linked to a higher risk for breast cancer.

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SOURCE: Cancer Epidemiology, Biomarkers & Prevention, published online Aug. 7, 2006