Antidepressants' link to birth defects small

Two new studies suggest that taking antidepressants during the first trimester of pregnancy may slightly increase the risk of some rare birth defects.

But the studies, published in today's New England Journal of Medicine, found that the overall risks are quite small. And scientists cautioned women against stopping treatment, saying untreated depression can be even more of a danger to their offspring.

"Overall, our results are generally reassuring with respect to the use of antidepressants during pregnancy," said Jennita Reefhuis, an epidemiologist at the Centers for Disease Control and Prevention (CDC) and one of the study authors.

The studies were designed to find out if a class of drugs known as SSRIs (selective serotonin-reuptake inhibitors) posed a risk to developing fetuses early in pregnancy. They were prompted, in part, by a 2005 study suggesting that Paxil increased the rate of heart defects from about 1 percent to 2 percent. Other drugs in that class include Prozac, Zoloft and Celexa.

Paxil maker GlaxoSmithKline sparked concern about SSRIs by issuing an alert in 2005 about possible heart defects in newborns whose mothers took Paxil early in pregnancy. The Food and Drug Administration then added its own warning.

Together, the two studies looked at 19,471 newborns with birth defects and 9,952 without them. They then considered what SSRIs the mothers in both groups took during the first three months of pregnancy and mapped the patterns of birth defects.

Neither study was able to tie SSRIs as a group to heart defects.

However, one of the reports associated Zoloft with a nearly sixfold increase in cases of omphalocele, in which intestines or other abdominal organs protrude from the navel. The birth defect is rare, occurring in one of every 5,000 births, according to federal statistics.

The finding was based on three cases in which infants with the intestinal defect were exposed to Zoloft — not enough to draw firm conclusions, said Carol Louik, a Boston University epidemiologist and lead author of the study.

The other study linked antidepressant use to a doubling of the risk of three congenital problems: anenecephaly, a defect in which a large portion of the brain and skull is missing; craniosynostosis, in which connections between skull bones close prematurely; and intestinal defects.

The researchers, from the CDC and the University of British Columbia in Vancouver, B.C., cautioned that their findings were based on a handful of cases.

"The take-home message is that we are talking about very small risks," said University of California, San Diego, epidemiologist Christina Chambers, who has studied the effects of antidepressants but wasn't involved in the new research.

Experts say every pregnancy carries about a 3 percent chance of serious birth defects. About 10 percent of women experience depression during pregnancy, according to one of the studies.

Left untreated, a woman's depression could lead to smoking, drinking and other behaviors that can harm fetuses. It also could lead to poor care, turmoil at home, a weaker maternal bond and other problems for a newborn.

"The fetus and the newborn are almost always worse off if the mom is depressed than if ... exposed to the vast majority of antidepressants," said Dr. Stephan Quentzel, a psychiatrist who treats pregnant women at Beth Israel Medical Center in New York.

Last year, a separate study linked SSRIs taken late in pregnancy to a lung disorder in newborns. The latest studies do not consider that disorder, known as persistent pulmonary hypertension.

Researchers said women should talk over the potential risks and benefits of antidepressant drugs with their doctors, preferably before pregnancy.

Compiled from The Associated Press, the Los Angeles Times and the (Minneapolis) Star Tribune