Depression during pregnancy is more common than most people believe, agree Dr. De-Kun Li, a reproductive perinatal epidemiologist in the research division at Kaiser Permanente in Oakland, Calif., and Dr. Diana Dell, a psychiatrist and obstetrician-gynecologist at Duke University Medical Center in Durham, N.C.
One or two of every 10 pregnant women have symptoms of major depression, according to the March of Dimes. Those who have had a bout of depression before are more likely to get it again. And Li said that others might have depressive symptoms -- short of clinical depression but still bothersome and unhealthy.
In his recent study of 791 pregnant women, Li found that 44 percent had depressive symptoms, about half of them severe, during pregnancy. "It wasn't necessarily clinical depression," he said, but a mood noticeably low.
Li tracked the women through delivery and found that those with depressive symptoms had nearly twice the risk of delivering a baby early, before 37 weeks.
Early delivery, by itself, is associated with health risks, he said. "Premature delivery is the No. 1 cause of infant mortality," he said. His findings were published in the January 2009 issue of Human Reproduction.
"We don't know the mechanism" of why depression and early delivery are linked, Li said. But what's certain is that "depression is not a benign condition," he said. "It can be harmful to your baby." What about antidepressant use during pregnancy? "What I tell patients who see me in consultation [for depression] is that moms need to be well in pregnancy," Dell said.