Pregnancy drug raised cancer odds in daughters

A drug that millions of pregnant women took decades ago to prevent miscarriage and complications has put their daughters at higher risk for breast cancer and other health problems that are showing up now, a new federal study finds.

Many of these daughters, now over 40, may not even know of their risk if their mothers never realized or told them they had used the drug, a synthetic estrogen called DES.

The new study suggests that infertility is twice as common and that breast cancer risk is nearly doubled in these daughters.

The sons of DES users also face health risks – testicular problems and cysts – but these are less well studied and don’t seem to be as common. Even less is known about the third generation – “DES grandchildren.”

In the United States alone, more than 2 million women and 2 million men are thought to have been exposed to DES while in the womb and may now want to talk with their doctors about when they should be screened for health problems.

“We don’t want to cause a panic of everyone rushing out thinking they’re going to get cervical or breast cancer. They just need to have that conversation with their physician,” said Dr. Sharmila Makhija, at the University of Louisville.

The average woman has about a 1 in 50 chance of developing breast cancer by age 55; for DES daughters it’s 1 in 25, the study found. Risks for other health problems vary.

DES, or diethylstilbestrol, was widely used in the United States, Europe and elsewhere from the 1940s through the 1960s to prevent miscarriage, premature birth, bleeding and other problems. Many companies made and sold it as pills, creams and other forms.

Studies later showed it didn’t work. The government told doctors to stop using it in pregnancy in 1971, after DES daughters in their late teens and 20s were found to be at higher risk of a rare form of vaginal cancer. Further research has tied DES to infertility and various pregnancy problems.

Results are in today’s New England Journal of Medicine.

The study started in 1992 and involved about 4,600 DES daughters and a comparison group of 1,900 similar women whose mothers had not used DES. Their health was tracked over time through surveys and medical records. Their average age at the last followup was 48.