It's been estimated that one-fifth to one-quarter of women experience an episode of depression during pregnancy, and for many women medication is needed to treat the symptoms. Researchers have begun to study the effects of a mother's antidepressant use during pregnancy on newborns, but results have been inconsistent. A recent population-based study performed at Aarhus University in Denmark found a link between mothers taking selective serotonin reuptake inhibitors (SSRIs) during the first trimester of pregnancy and septal heart defects in their infants.

The researchers examined the records pertaining to almost 500,000 singleton births from 1996 to 2003 in Denmark, comparing rates of birth defects in the infants of 493,113 women who hadn't taken SSRIs with those in 1,370 women who had filled at least two prescriptions for SSRIs during the first trimester of pregnancy.

The study found no correlation between SSRI use and major malformations such as omphalocele or craniosynostosis, but infants of women who used sertraline (Zoloft) and citalopram (Celexa) had a greater chance of having septal heart defects (odds ratios, 3.25 and 2.52, respectively). Filling prescriptions for more than one SSRI was associated with an even higher risk of septal heart defects (odds ratio, 4.70).

It's important to note that despite greater odds of developing a condition, the absolute differences in prevalence can be quite small. For instance, the prevalence of septal heart defects among infants exposed to one SSRI was 0.9%, whereas among unexposed children it was 0.5%. According to the study authors, the "number needed to treat to harm" was 246, meaning that for every 246 women who filled two prescriptions for SSRIs during the first trimester, there would be one septal heart defect. That number dropped to 62 when the women took more than one type of SSRI.

That doesn't mean there isn't risk, however. "We believe that the data, interpreted in the context of earlier studies, suggest a class effect of SSRIs on heart defects," said Lars Henning Pedersen, one of the authors of the study, in an e-mail. "Our results seem overall to be in accordance with two large and well-performed American studies."

Results such as these underscore how important it is for clinicians to weigh the possible adverse effects of SSRIs against the severity of the mother's depression, said Donna Patno, a nurse midwife at the Cleveland Clinic.

"We're quick to treat hypertension and diabetes, and sometimes depression does require judicious use of medication," she said. "But women need to understand that there is help out there, even if we don't use medication. We need to empower women to make a choice and use our good clinical judgment."

Tammy Worth