Taking Medication While Pregnant
Safe or Sorry?
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
"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
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.