Americans take more antidepressants than they do any other type of prescription drug, and pregnant women are no exception. One out of every eight pregnant women in the U.S. takes selective serotonin re­up­take inhibitors (SSRIs) to treat depression or other mood disorders. A handful of recent studies suggest that these drugs could have adverse effects on infant health: they may increase the risk for rare heart defects, premature delivery, low birth weight and withdrawal symptoms. Nevertheless, some doctors argue that the benefits these drugs provide still outweigh the potential risks.

Worries over the use of SSRIs during pregnancy first surfaced in journal articles published in the 1980s, but it was not until 2005 that the U.S. Food and Drug Administration conceded that babies born of mothers who take paroxetine (sold as Paxil and Seroxa) during their first trimester are up to twice as likely to exhibit fetal heart defects. A 2005 study published in the Lancet also found that some newborns born of mothers taking paroxetine suffer from withdrawal symptoms such as convulsions and abnormal crying for several days.

More recently, pregnancy risks associated with other SSRIs have also come to light. A study published in the September 26 issue of the British Medical Journal monitored nearly 500,000 Danish children from nationwide registries and found that women who take sertraline (Zoloft), citalopram (Celexa) and fluoxetine (Prozac) are more likely to give birth to babies with heart defects, although the overall risk is still quite low. A study in press in the Journal of Clinical Psychopharmacology notes that women treated with SSRIs during late pregnancy are more likely to give birth to small and premature babies. A study published in the October 2009 Archives of Pediatric and Adolescent Medicine suggests that women taking SSRIs are twice as likely to have preterm births as compared with the general population and that their babies are more likely to spend time in the neonatal intensive care unit.

So should women stop taking SSRIs when they are pregnant? Not necessarily, says Emilio Sanz, a clinical pharmacologist at the University of La Laguna in Tenerife, Canary Islands, and co-author of the 2005 Lancet study. He notes that untreated depression increases the risk of prematurity, low birth weight and neonatal complications, too. Sengwee Darren Toh, an epidemiologist at the Harvard School of Public Health, points out that these similar outcomes make it “quite difficult to tease out effects of the drugs from those of underlying depression.”

Sanz and Toh point out, however, that many women who take SSRIs have not been diagnosed with clinical depression—some take the drugs for obsessive-compulsive disorder, pain management or even severe premenstrual symptoms. For these kinds of conditions, there may be other, potentially safer options. For instance, in September 2009 a report from the American Psychiatric Association and the American College of Obstetricians and Gynecologists argued that psychotherapy is a suitable treatment for some pregnant women suffering from mild forms of depression or other mood disorders. Doctors have to “distinguish between real depression and just blues, sadness, feeling down,” Sanz says.