Oct. 5, 2009 -- New research provides further evidence that links antidepressant use among pregnant mothers to problems for their newborns at birth.

The study showed that exposure to selective serotonin reuptake inhibitors (SSRIs) is associated with babies born an average of five days earlier and with twice the rate of premature births as infants whose mothers had no history of psychiatric illness.

Premature birth -- also known as preterm birth -- is commonly defined as happening before the baby has reached 37 weeks and happens in about 12% of all pregnancies. Cognitive problems, breathing problems, cerebral palsy, and digestive problems are all associated with preemie births.

Newborns whose mothers took SSRIs while expecting were also more than twice as likely to be admitted to the neonatal intensive care unit (NICU) and to have a lower 5-minute Apgar score than babies whose mothers did not take the drugs during pregnancy, according to the study. The Apgar score is a shorthand method of rating a newborn’s health status immediately after birth.

“Based on these results, we can say that there is an effect of SSRIs taken during pregnancy,” says lead researcher Najaaraq Lund, MD. “But whether or not this should be a reason for avoiding SSRIs? We still don’t have a final answer,” says Lund, who was a medical student researcher at the University of Aarhus in Denmark at the time the study was conducted.

SSRIs are the most common class of antidepressants taken by pregnant women in the U.S. The American College of Obstetricians and Gynecologists (ACOG) estimates that between 14%-23% of all pregnant women experience some form of depression during pregnancy.

In the study, Lund’s team used health records of more than 56,000 women who received prenatal care from the University of Aarhus Hospital between 1989 and 2006. The vast majority of these women had no psychiatric illness, but about 300 of them had received SSRIs during their pregnancy and nearly 5,000 of the study participants had a history of psychiatric problems but did not take any SSRIs while being treated for their pregnancy.