DES - Diethylstilbestrol

by National Cancer Institute

1. What is DES?

DES (diethylstilbestrol) is a synthetic form of estrogen, a female hormone. It was prescribed between 1940 and 1971 to help women with certain complications of pregnancy. Use of DES declined in the 1960s after studies showed that it is not effective in preventing pregnancy complications. When given during the first 5 months of a pregnancy, DES can interfere with the development of the reproductive system in a fetus. For this reason, although DES and other estrogens may be prescribed for some medical problems, they are no longer used during pregnancy.

2. What health problems might DES-exposed daughters have?

In 1971, DES was linked to an uncommon cancer (called clear cell adenocarcinoma) in a small number of daughters of women who had used DES during pregnancy. This cancer of the vagina or cervix usually occurs after age 14, with most cases found at age 19 or 20 in DES-exposed daughters. Some cases have been reported in women in their thirties and forties. The risk to women older than age 40 is still unknown, because the women first exposed to DES in utero are just reaching their fifties, and information about their risk has not been gathered. The overall risk of an exposed daughter to develop this type of cancer is estimated to be approximately 1/1000 (0.1 percent). Although clear cell adenocarcinoma is extremely rare, it is important that DES-exposed daughters be aware of the risk and continue to have regular physical examinations.

Scientists found a link between DES exposure before birth and an increased risk of developing abnormal cells in the tissue of the cervix and vagina. Physicians use a number of terms to describe these abnormal cells, including dysplasia, cervical intraepithelial neoplasia (CIN), and squamous intraepithelial lesions (SIL). These abnormal cells resemble cancer cells in appearance; however, they do not invade nearby healthy tissue as cancer cells do. These abnormal cellular changes usually occur between the ages of 25 and 35, but may appear in exposed women of other ages as well. Although this condition is not cancer, it may develop into cancer if left untreated. DES-exposed daughters should have a yearly Pap test and pelvic exam to check for abnormal cells. DES-exposed daughters also may have structural changes in the vagina, uterus, or cervix. They also may have irregular menstruation and an increased risk of miscarriage, tubal (ectopic) pregnancy, infertility, and premature births.

3. What health problems might DES-exposed sons have?

There is some evidence that DES-exposed sons may have testicular abnormalities, such as undescended testicles or abnormally small testicles. The risk for testicular or prostate cancer is unclear; studies of the association between DES exposure in utero and testicular cancer have produced mixed results. In addition, investigations of abnormalities of the urogenital system among DES-exposed sons have not produced clear answers.

4. What health problems might DES-exposed mothers have?

Women who used DES may have a slightly increased risk of breast cancer. Current research indicates that the risk of breast cancer in DES-exposed mothers is approximately 30 percent higher than the risk for women who have not been exposed to this drug. This risk has been stable over time, and does not seem to increase as the mothers become older. Additional research is needed to clarify this issue and whether DES-exposed mothers are at higher risk for any other types of cancer.

5. How can people find out if they took DES during pregnancy or were exposed to DES in utero?

It has been estimated that 5 to 10 million people were exposed to DES during pregnancy. Many of these people are not aware that they were exposed. A woman who was pregnant between 1940 and 1971 and had problems or a history of problems during pregnancy may have been given DES or a similar drug. Women who think they used a hormone such as DES during pregnancy, or people who think that their mother used DES during pregnancy, can contact the attending physician or the hospital where the delivery took place to request a review of the medical records. If any pills were taken during pregnancy, obstetrical records should be checked to determine the name of the drug. Mothers and children have a right to this information.

However, finding medical records after a long period of time can be difficult. If the doctor has retired or died, another doctor may have taken over the practice as well as the records. The county medical society or health department may know where the records have been stored. Some pharmacies keep records for a long time and can be contacted regarding prescription dispensing information. Military medical records are kept for 25 years. In many cases, however, it may be impossible to determine whether DES was used.

6. What should DES-exposed daughters do?

It is important for women who believe they may have been exposed to DES before birth to be aware of the possible health effects of DES and inform their doctor of their exposure. It is important that the physician be familiar with possible problems associated with DES exposure, because some problems, such as clear cell adenocarcinoma, are likely to be found only when the doctor is looking for them. A thorough examination may include the following:

Pelvic examination — A physical examination of the reproductive organs. An examination of the rectum also should be done.

Palpation — As part of a pelvic examination, the doctor feels the vagina, uterus, cervix, and ovaries for any lumps. Often palpation provides the only evidence that an abnormal growth is present.

Pap test — A routine cervical Pap test is not adequate for DES-exposed daughters. The cervical Pap test must be supplemented with a special Pap test of the vagina called a "four-quadrant" Pap test, in which cell samples are taken from all sides of the upper vagina.

Iodine staining of the cervix and vagina — An iodine solution is used to temporarily stain the linings of the cervix and vagina to detect adenosis (a noncancerous but abnormal growth of glandular tissue) or other abnormal tissue.

Colposcopy — In colposcopy, a magnifying instrument is used to view the vagina and cervix. Some doctors do not perform colposcopy routinely. However, if the Pap test result is not normal, it is very important to check for abnormal tissue.

Biopsy — Small samples of any tissue that appears abnormal on colposcopy are removed and examined under a microscope to see whether cancer cells are present.

Breast examinations — Researchers are studying whether DES-exposed daughters have a higher risk of breast cancer than unexposed daughters; therefore, DES-exposed daughters should continue to follow the routine breast cancer screening recommendations for their age group.

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