The children of mothers with long-term depression have been found to be at higher risk of behavioural problems and poor development.
University of Queensland researchers analysed depression levels in 892 mothers and the development and behaviour of 978 children, using data from the Australian Longitudinal Study on Women's Health.
They compared maternal depression before, during and after pregnancy, and found duration was more influential than timing.
Researcher Dr Katrina Moss said the study found one in five women experienced depression once, while 11 per cent experienced a reoccurrence.
"The longer a mother suffered maternal depression, the worse the outcomes for the child," Dr Moss said.
"Mothers may worry that if they've been depressed during pregnancy then it's too late to do anything about it, but reducing depressive symptoms at any stage is better for them and their children.
"The earlier we can effectively detect and treat maternal depression, the better our chances of improving outcomes."
Dr Moss suggested screening for depression could start when couples begin planning a pregnancy, and continue through the perinatal period and early childhood.
"Maternal depression is a significant challenge for women, families and communities, and we need to look after women better at key times in their lives," she said.
Dr Moss said women experiencing depression should visit their GP and use supportive parent resources from organisations such as PANDA or the Gidget Foundation.