One in eight women is depressed during pregnancy, which can impact on the health of their unborn child, a study has found.
The Growing Up in New Zealand study released on Monday analysed interviews with 5664 women during their last months of pregnancy.
Women suffering from depression can struggle to look after themselves, which can increase the risk of premature birth and delay the child's motor and emotional development, researchers found.
"Women affected by antenatal depression are more likely to smoke and eat poorly, resulting in too much or not enough weight gain which can affect the baby's development," said Auckland University associate Professor Karen Waldie.
"These women are also less likely to make use of maternity services or breastfeed, and have a higher risk of experiencing depression after their child is born," the psychosocial and cognitive expert adviser for the study said.
Doctors and midwives needed to improve their recognition and treatment of depression and researchers hope the study will help them recognise the characteristics.
"Symptoms such as sleep disruption, low energy or a change in appetite are often misinterpreted as a normal aspect of pregnancy, which makes it more difficult to recognise a mother with antenatal depression," Dr Waldie said.
New Zealand doesn't screen for antenatal depression and the high number of cases might justify reconsidering that, she said.
Growing Up in New Zealand is a longitudinal study tracking about 7000 children from before birth.