Effects of Teratogenic Drugs during Pregnancy

If anyone ever doubted that drugs taken by the mother, with minimal maternal effects, could be disastrous for the fetus, the frightening experiences with thalidomide and DES (diethylstilbestrol) dispelled this. Thalidomide was introduced in Europe in the 1960s as a mild sedative to encourage sleep. Unfortunately, pregnant women often have difficulty sleeping and many of them took the drug. Within a year the disaster became obvious.

Large numbers of malformed babies were born. They had one form or another of what is technically referred to as phocomelia . The children lacked long bones in their arms and legs and had flippers for hands and feet. The unfortunate experience with DES came to light in the early 1970s. This synthetic estrogen was given to women who had a multitude of problems with their pregnancies.

Motivated by the mistaken expectation that it would improve the outcome of pregnancy, doctors prescribed DES for pregnant women who had diabetes and bleeding. It was given early in pregnancy to women who had previous miscarriages or unexplained second-trimester pregnancy losses. Four to six million pregnant women were treated with varying amounts of DES for varying durations of their pregnancies during a period of over twenty years, from the late 1940s into the early 1970s. Articles doubting the benefit of DES appeared in medical journals as early as 1953. Yet, the adverse effects of DES on the daughters of women who took the drug during pregnancy did not make themselves known until the daughters were well into adolescence, explaining the 20-year delay in identifying the problems DES produced.

Researchers took even longer to verify the less noticeable changes in the sons, a small percentage of whom have some anatomic abnormalities. The first DES warning was the appearance in Boston of an unusual kind of cancer of the vagina among young women. This unusual cancer had been seen before in older women, but the occurrence over a short time in a substantial number of adolescents pointed to an environmental cause.

Investigators rapidly made the connection with DES given to the mothers. The epidemic of cancer among DES daughters appears to be over, although whether there will be additional carcinogenic effects as this group of women ages remains unknown. In addition to various nonmalignant changes in the anatomy of the vagina, cervix, and uterus, a number of DES daughters have had difficulty becoming pregnant or maintaining their pregnancies. They have more frequent miscarriages, ectopic pregnancies, and premature labors . If you were born before 1972 and think you may be a DES daughter, ask your mother whether she took any drugs during her pregnancy. Since memory is inexact and since DES-type drugs were marketed under numerous trade names, also ask your physician or midwife to examine you specifically to look for the typical anatomic changes produced by DES.

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