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Taking Medication While Pregnant

Safe or Sorry?
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Teratogens: The Tests of Time continued...

The U.S. Food and Drug Administration requires manufacturers to test drugs that might be used by reproductive-age women in pregnant animals, but the reactions in animals aren't always the same. Thalidomide, a sedative and antinausea drug used by pregnant women in Europe, produced limb deformities in nearly 6,000 babies born between 1956 and 1963, but did not affect pregnant rats. Fortunately, the drug was not approved in the United States.

Yet over the years, experts have accumulated data on the effects of an array of medications used by women during pregnancy. One of the largest such studies, published in the late 1970s, tracked 50,282 pregnant women who took a variety of drugs from 1958 to 1965. Drugmakers also must report any problems they find out about to the Food and Drug Administration, and doctors voluntarily do the same.

What scientists have found so far is that only a relatively small number of medications are known teratogens, substances that cause abnormalities in the growing fetus. About one out of every 33 babies is born with birth defects each year; about 2% to 3% of those are believed to be from drug exposure.

"There are very few medications you shouldn't take," says Jennifer Niebyl, MD, head of obstetrics and gynecology at University of Iowa College of Medicine, who has written chapters in medical textbooks on drugs during pregnancy. "Obviously you should check with your healthcare provider first, but if a mother needs medicine for medical illness, she should take it."

The FDA uses the data that's accumulated to classify drugs based on teratogenic risk. There are currently five categories: A, B, C, D and X. Type A drugs are the least harmful, and X have risks that clearly outweigh any benefits. The agency is considering a change to these categories to give doctors and the public a clearer picture of the data available.

In addition to the FDA lists, about 20 teratogen centers throughout the country are constantly updating a database of information on the effects of different drugs in pregnant women. "Having your doctor call and check with a hotline for the most recent information is a really rational thing to do," Filkins advises.

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