According to a new study published in Human Reproduction, women who were severely depressed during early pregnancy were twice as likely to have a preterm delivery. The worse the depression the greater was the risk of giving birth prematurely, the leading cause of infant mortality.

The researchers interviewed 791 San Francisco-area women near their 10th week of pregnancy, all of them were members of the Kaiser Permanente Medical Care Program, a managed-care plan.  They noted that 41 % reported "significant" symptoms of depression, while 22 % reported "severe" symptoms. The women with severe symptoms were twice as likely to deliver a premature baby before 37 weeks' gestation while those with significant symptoms had a 60 % risk of early birth, the study found.

De-Kun Li, M.D., Ph.D., the lead study author and a reproductive and perinatal epidemiologist at Kaiser Permanente's Division of Research in Oakland, California said, "Don't think, 'This is just part of being pregnant, this is my hormones doing something.'" He said depression relief doesn't always have to be via medication. "Getting the emotional and physical support of your family members can significantly alleviate symptoms of depression."

According to the March of Dimes 12.5 % of the babies born in the United States every year are premature and these babies can suffer from many medical and learning problems. Despite decades of research, doctors still have no way to determine who's at risk nor do they understand why it happens or how to prevent it.

 Li said, "We don't know what is going on. If we can find something as obvious as depression that can be treated during pregnancy, that is very, very significant.  Depression during pregnancy really has not been paid attention to," Dr. Li says. "It's definitely under diagnosed, undertreated, and frequently dismissed and ignored."

The study also noted that the women who were younger than 25, unmarried, less educated, poorer, black, and have a history of preterm delivery, were likelier to report depressive symptoms.

Diane Ashton, M.D., deputy medical director of the March of Dimes in White Plains, New York said, "Women who are depressed also have a lot of other factors that can put them at risk for preterm birth." Poor diet and smoking being the main culprits. "What I tell my patients is that they need to be well during pregnancy," says Diana L. Dell, M.D., an assistant professor in obstetrics and gynecology as well as psychiatry at Duke University in Durham, N.C. "That's what the study is basically showing us.” For women with mild to moderate depression, therapy is often enough, according to Dr. Dell. But medication might be necessary for women with more severe depression.