Women who are depressed early in pregnancy may double the chances of delivering a baby earlier than 37 completed weeks of pregnancy, a new study suggests.

Researchers followed 791 women during their pregnancy, the Human Reproduction journal said. The two fifths of participants in the study who were suffering from significant depression symptoms around the 10th week of pregnancy had twice the risk of delivering preemies.

Whereas expectant women with severe depression had twice the risk of giving birth to babies before 37 weeks gestation, mild depression led to even higher risk - 60 percent.

Taking into account the findings, researchers drew the conclusion that there is a direct link between the risk of preterm delivery and early-pregnancy depression. They added that most heavy with child women in the study hadn’t taken antidepressant drugs, suggesting that side effects from the medications couldn’t justify the connection between the two.

So, women should know that antenatal depression shouldn’t be dismissed as something natural, lead author De-Kun Li, a reproductive and perinatal epidemiologist at Kaiser Permanente's Division of Research in Oakland, California, said in an interview.

Depression during pregnancy is a serious medical condition which may jeopardize the health of the woman and her baby. It is considerably “under-recognised and under-diagnosed - clinicians should pay close attention to catch it early," Dr De-Kun Li said.