In this study, the researchers wanted to learn whether women exposed to DES before birth (in the womb), known as DES Daughters, were more likely to develop cancer than unexposed women. Cancer rates of DES Daughters were also compared with cancer rates among women in the general population whose DES exposure status was unknown. At the time of this study, researchers accepted that DES exposure before birth increased a woman's risk of developing clear cell adenocarcinoma (CCA) of the vagina and cervix. However, researchers were not certain whether the risk for other types of cancer also increased.

Over a 16-year period, the researchers compared the medical histories of 3,650 DES Daughters with those of 1,202 unexposed women. The researchers then compared cancer rates from the two study groups to cancer rates for women in the general population whose DES exposure status was not known.

The researchers found that for DES Daughters, the rate for all types of cancer (other than CCA) was similar to the rates for unexposed women and women in the general population. In addition, DES Daughters were 40 times more likely than women in the general population to develop CCA.

Although this study was one of the largest of its kind, the study had some limitations. For example, the average age of DES Daughters who participated was 24 at the start of the study and 38 at last follow-up. The researchers suggested continued study of these DES Daughters for any increased cancer risks during menopausal years.

Another limitation of this study concerned breast cancer. Many studies have demonstrated that women exposed to estrogen in high doses or over a long period of time have an increased risk for breast cancer. However, breast cancer is most likely to occur in older women. Thus, the women in this study will have to be monitored over the next several decades to determine whether DES Daughters develop breast cancer at higher rates than do unexposed women.

Citation: Hatch EE, Palmer JR, Titus-Ernstoff L, Noller KL, Kaufman RH, et al. Cancer risk in women exposed to diethylstilbestrol in utero. JAMA 1998;280:630-4.