Monday July 19 6:09 PM ET
NEW YORK, Jul 19 (Reuters Health) -- The daughters of women who used the drug diethylstilbestrol (DES) during the 1940s-1970s are at increased risk for cancer of the uterus, cervix and other reproductive organs. Now, studies in mice suggest that these risks may extend to granddaughters, as well.
The finding ``indicates for the first time some sort of genetic mechanism at work,'' explained Nora Cody, executive director of DES Action, an information resource group for those exposed to DES. Cody spoke to Reuters Health from Washington, DC, site of this week's DES Research Update Conference, sponsored by the National Institutes of Health.
DES, a synthetic form of estrogen, was introduced in 1941 as a drug that prevented miscarriage. It was used by an estimated 2.4 million US women until its ban for use during pregnancy in 1971.
The drug appears to cause structural changes in the reproductive organs of both female and male children exposed to DES before birth. Studies suggest that almost half of all DES-exposed daughters will experience complications in pregnancy (such as ectopic pregnancy or miscarriage) associated with DES-induced malformations.
Research has also indicated that women exposed to DES via their mothers have an especially high risk of clear cell adenocarcinoma of the vagina and/or cervix -- an otherwise rare genital cancer.
Risks to the granddaughters of DES users have, until recently, remained unclear. However, researchers led by Dr. Retha Newbold of the National Institute of Environmental Health Sciences, have recently reported that 11% of third-generation mice bred from DES-exposed grandmothers went on to develop ''malignant reproductive tract tumors.''
According to Cody, the finding ``gives much greater urgency to the question of what's happening in humans. We don't know for sure, but this gives us a strong suspicion that (DES-linked cancer risk) may continue into the third, fourth generations,'' she explained.
Cody stressed that many daughters and granddaughters of DES-users remain unaware of their exposure to the drug. ``If you were born between 1938 and 1971, you could be exposed to DES,'' she said.
Women should ask their mothers about possible exposure as soon as possible, she advised. ``The longer we wait, the worse it gets,'' Cody explained. ``These are events of a long time ago, (and in many cases) the mothers are dying or they just don't remember.''
Once a woman has determined that she has been exposed to DES, she should inform her doctor -- especially her obstetrician. ``It is recommended that all DES daughters be regarded as 'high-risk' pregnancy cases,'' Cody explained, ``and that means that they need to be seen more often.'' Studies have linked DES to an increased risk of miscarriage, premature birth, or tubal pregnancy in women whose mothers took the drug.
Sons can also be affected by a mother's DES exposure. Although studies have not yet found any increase in cancer risk among DES sons, they have confirmed higher rates of genital malformations such as undescended or small-sized testicles.
Cody said congressional legislation passed last fall reauthorized funding for DES research, and plans are under way to create a 'National DES Education Program.'
She believes that healthcare professionals need to be a target of that education effort. Many doctors' view of DES was formed by previous studies, she explained, which suggested that risks for reproductive cancer fell to normal levels after DES daughters passed 30 years of age. ``What we've discovered... over the past few years is that a lot of women in their 40s are getting this cancer, and we now know that there's no upper age limit on it,'' Cody said. ``Doctors and nurses really need to get that message.''