WEDNESDAY, Oct. 5, 2011 (HealthDay News) -- Women whose mothers were given the drug diethylstilbestrol (DES) during pregnancy are at increased risk for fertility problems and cancer as they age, new research shows.
This study from the U.S. National Cancer Institute "illustrates that the effects of intrauterine exposure to biologically active agents may take many decades to be fully appreciated or recognized in humans," said Dr. William Rodgers, chairman of pathology at Lenox Hill Hospital in New York City.
Use of DES -- the first synthetic form of estrogen -- to prevent certain types of pregnancy complications began around 1940. Research in the 1950s showed that DES didn't prevent these complications, and in the late 1960s, exposure to DES in the womb was linked to a rare cancer of the vagina (clear cell adenocarcinoma) among daughters of women who took the drug.
In 1971, the U.S. Food and Drug Administration said DES should not be given to pregnant women. But by that time, between 5 million and 10 million moms-to-be and their babies had been exposed to the drug.
In this study, NCI researchers looked at 4,600 women who were exposed to DES in the womb and 1,900 who were not exposed to the drug. They found that those with DES exposure were at increased risk for 12 medical conditions, including a more than doubled risk of infertility and a nearly fivefold increased risk of having a preterm delivery.
Among DES-exposed women, one in five will have some level of infertility, the study found. Of those who have at least one child, one in three will have a preterm delivery.
The researchers also found that DES-exposed women are about 40 times as likely as unexposed women to develop clear cell adenocarcinoma. However, the disease is still uncommon, with clear cell adenocarcinoma occurring in one of 1,000 DES-exposed daughters.
DES-exposed women are also more than twice as likely to develop pre-cancerous cells in the cervix or vagina, and 80 percent more likely to develop breast cancer after age 40.
By age 55, one in 25 DES-exposed women will develop abnormal cellular changes in the cervix or vagina, and one in 50 will develop breast cancer, according to the study.
"The risks were greatest in women with the largest DES exposure or who had changes in vaginal epithelium known to be caused by in utero exposure to DES," said Rodgers, who was not involved in the study. This strongly suggests that the DES exposure caused the reproductive problems, he said.
"Additional research will be needed to explain at a cellular level how DES exposure in utero produces these varied adverse reproductive outcomes," Rodgers said.
The study appears in the Oct. 6 issue of the New England Journal of Medicine.
The researchers didn't look at men who were exposed to DES in the womb, but previous studies indicate they may be at increased risk for testicular abnormalities.
More information
The U.S. National Cancer Institute has more about DES.
