Pregnant women who had untreated major depression in all three trimesters of pregnancy, as well as those who took certain antidepressants, had preterm birth rates exceeding 20 percent, according to a study by University of Pittsburgh School of Medicine researchers published in the March issue of American Journal of Psychiatry.

Approximately 10-to-20 percent of women struggle with symptoms of major depression during their pregnancies, but treating it can be complicated. Selective serotonin reuptake inhibitor (SSRI) antidepressants are usually the first line of depression treatment, but can lead to unwanted outcomes such as preterm births if used continuously throughout pregnancy, the findings suggest.

"It is well-known that the prevalence of depression in women is highest during the childbearing years, and treating the symptoms with SSRIs is a common medical therapy," said Katherine L. Wisner, M.D., M.S., director of the Women's Behavioral HealthCARE program at Western Psychiatric Institute and Clinic of UPMC, associate investigator at Magee-Womens Research Institute, and professor of psychiatry, obstetrics, gynecology and reproductive sciences and epidemiology at the University of Pittsburgh School of Medicine. "However, given the similarity in outcomes we found for continuous SSRI treatment and continuous depression, it is possible that underlying depressive disorder is a factor in preterm birth among women taking SSRIs."

Throughout this prospective study, researchers followed 238 women with no, partial, and continuous exposure to either depression or SSRI treatment during pregnancy and compared neonatal outcomes. They found that women exposed to either continuous SSRI treatment, or to continuous depression with no SSRI treatment, had comparable levels of increased risk for preterm birth at 21 percent and 23 percent, respectively. However, women with no exposure to either depression or SSRI medication had lower rates of preterm births, around 6 percent.

The researchers also discovered that either depression or SSRI treatment did not affect the baby's birth weight or the mother's weight gain during pregnancy or influence the rate of minor physical birth defects in the infant.

Previous studies have associated both depression and SSRIs with an increased risk for miscarriage. But taking these antidepressants during pregnancy does not greatly increase the overall risk of birth defects, noted Dr. Wisner.

While the results add more evidence linking SSRI treatment to risk of preterm birth, the risk of untreated depression conveys no less risk and suggests that factors independently related to both the disease and its treatment are associated with preterm birth.

"The relationship of preterm birth to depression and SSRI exposure must be clarified through further research," said Dr. Wisner. "In the meantime, it is recommended that each pregnant woman consult with her doctor to weigh the benefits and risks of depression treatment with antidepressants."