DES and Pregnancy

Examining the Reproductive Challenges: Looking at a Study Analyzing the Impact of Prenatal DES Exposure on DES Daughters’ Fertility, Pregnancy, and Maternal Health

A critical study by researchers with the National Cancer Institute DES Follow-up Study was published in the October 2011 New England Journal of Medicine. The research team analyzed the data from three long-term studies on the adverse outcomes experienced by women exposed to DES. The findings illustrate why so many DES Daughters have had difficulties seeing their pregnancies through to delivery.

Table from Hoover RN, Hyer M, Pfeiffer RM, et al. Adverse health outcomes in women exposed in utero to diethylstilbestrol. N Engl J Med. 2011;365:1304–1314.

Structural Changes of the Reproductive Tract

DES Daughters have an increased incidence of structural changes in their reproductive organs, including a T-shaped uterus (see illustration below). The uterine lining of a T-shaped uterus appears to be the same as that of women who were not exposed, so researchers suggest the fundamental difference aside from the shape is in the underlying fibromusculature. Of note, the study found that pregnant DES Daughters have a significantly increased risk of premature delivery, whether they have a T-shaped uterus or not.

Prenatal DES exposure can adversely affect the shape and functioning of virtually the entire reproductive tract, including the vagina, cervix, uterus, fallopian tubes, and ovaries. Some DES Daughters report having an incompetent cervix, which can be the cause of second-trimester pregnancy losses.

Illustration: cdc.gov

Infertility

DES Daughters have an increased risk for infertility, with studies showing a 33% infertility rate after 12 months for DES Daughters compared with 15.5% for unexposed women in the same time frame. Generally, infertility treatments for DES Daughters are the same as for other women.

Ectopic Pregnancy

Ectopic (or tubal) pregnancies occur when the egg implants and develops in a location outside of the uterus, most often in the fallopian tube. These complicated pregnancies were seen about 14.6% of the time in DES Daughters compared with less than 3% in those of unexposed women.

Because of this increased risk, DES Daughters should have early confirmation of pregnancy with a blood test and ultrasound to be certain the fetus is developing inside the uterus. An ectopic pregnancy is a potentially life-threatening condition that is best handled when identified early.

Menstruation, Miscarriage, and Preterm Labor

The 2011 analysis demonstrated that DES Daughters experienced preterm delivery at the not-insignificant rate of 53.3% compared with 17.8% for unexposed women. Miscarriages have been shown to occur in 50.3% of DES Daughters compared to 38.6% in unexposed women.

Most early miscarriages are not preventable. However, careful monitoring of the cervix during these “high-risk” pregnancies is warranted.

To reduce the risk of late miscarriage or preterm delivery, a DES Daughter will be closely monitored and learn to observe for possible early contractions.

Understanding the cause of a threatened second-trimester pregnancy loss is important. Some second-trimester losses occur in DES-exposed women because of an incompetent cervix, while others are the result of premature labor. This is an important distinction since treatments employed in these conditions are different.

Sometimes, a stitch called a cerclage is inserted into the cervix to keep it closed if an incompetent (weak) cervix is the problem. In the case of preterm labor, the doctor may recommend bed rest or specific drugs that suppress the contractions, and a cerclage would be of no use. Of course, DES Daughters are urged to accept medications cautiously and learn why they are being prescribed, how they work, and what side effects are known.

According to a 2018 study on third-generation DES exposure that appeared in Reproductive Toxicology, DES Granddaughters also have an increased incidence of reproductive-related complications. They were shown to have a higher risk of irregular menstruation and preterm delivery than other women in the population whose mothers were not DES Daughters. This study was further reviewed here in the VOICE Winter 2020.

DES Granddaughters should make their doctors aware of these findings if they are pregnant or planning a pregnancy. They should receive high-risk obstetric care.

Preeclampsia

Preeclampsia is a condition that occurs during pregnancy involving high blood pressure and edema (fluid retention). The 2011 study also showed that this happens to DES Daughters about 26.4% of the time versus 13.7% in unexposed pregnant women. Additionally, earlier evidence had suggested that preeclampsia among DES Daughters is more often seen when the uterus is abnormally shaped.

Bottom Line

Because of the increased risks for these complications, all DES Daughters (and perhaps even Granddaughters), require high-risk obstetric care – starting as early as possible even if they’ve had previous normal pregnancies.

Please see the DES Daughters and the DES Grandchildren pages for additional health information.

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