New mothers with diabetes may have nearly twice the risk of experiencing depression during pregnancy and after they give birth, which puts both the mother and baby at risk, researchers say.

Depression during the last several months of pregnancy and the year following childbirth, the perinatal period, affects at least 10 to 12 per cent of new mothers. Between two per cent and nine per cent of pregnancies are complicated by diabetes, according to the study.

In Wednesday's issue of the Journal of the American Medical Association, Katy Backes Kozhimannil of Harvard medical school in Boston and her colleagues looked at the link between diabetes and depression among 11,024 women with low incomes who gave birth between July 2004 and September 2006.

Women with diabeteswere nearly twice as likely of having a depression diagnosis or taking an antidepressant medication (15.2 per cent) compared with those without diabetes (8.5 per cent), after taking into account age, race, year of delivery and preterm birth.

"Pregnancy and the postpartum period represent a time of increased vulnerability to depression. Treatable, perinatal depression is underdiagnosed, and it is important to target detection and support efforts toward women at high risk," the study's authors wrote.

"Among all women with depression, diabetes, or other mental or physical health conditions that complicate the normal course of pregnancy and postpartum recovery, careful monitoring and appropriate treatment are critical to ensuring the health of the mother and her child."

The link remained regardless of the type of diabetes, including gestational diabetes that develops during pregnancy.

Postpartum depression is risky if not addressed, but both depression and diabetes are treatable.