Depression is more common in first-time mothers when the child is four years old than at any time during the 12 months after giving birth, according to a new study.

Research carried out in Australia has shown almost one in three first-time mothers reported depressive symptoms at least once between pregnancy and four years after giving birth.

But the study, published in BJOG: An International Journal of Obstetrics and Gynaecology, found depressive symptoms were more common four years after a first birth than at any time during the first 12 months of a baby’s life.

The study used data from 1,507 first-time mothers registered to give birth at six hospitals in Melbourne, Australia, who completed questionnaires at three, six, 12, 18 months and four years after giving birth.

There also needs to be a focus on social health and relationships as we have found a strong link between depressive symptoms and intimate partner violence

Women with only one child at four years after birth showed significantly higher levels of depression than women with two or more children.

The strongest predictor of depressive symptoms at four years post birth were having previously reported depressive symptoms either in early pregnancy or in the first 12 months after childbirth. Other factors associated with depressive symptoms were being young – 18 to 24 years old – stressful life events in the year before the four-year follow-up, violence from a partner or a low income.

But at four years after giving birth, 40 per cent of women reporting depressive symptoms had not previously reported this.

The authors of the report said the findings presented a “compelling” case for a rethink on approaches to monitoring maternal mental health where policies focus on pregnancy and the early months after birth.

Hannah Woolhouse, psychologist and senior research officer, from the Murdoch Children’s Research Institute, in Victoria, Australia and co-author of the report, said: “It is likely that current systems of maternal mental health surveillance in Australia and the UK will miss more than half the women experiencing depression in the early years of parenting.

“In particular, women who do not have subsequent children may be especially vulnerable to falling through the gaps as they will not be reconnected back into primary care services.

“There also needs to be a focus on social health and relationships as we have found a strong link between depressive symptoms and intimate partner violence.”

John Thorp, BJOG editor in chief, said: “Much research has been conducted around maternal mental health during the perinatal period, however, we know very little about the prevalence of maternal depression after the first 12 months of giving birth.

“The findings of this study reinforce the need for an increased focus on maternal health, particularly in the long term, as current guidance for professionals focuses on pregnancy and the early months after birth, and the need to take into account factors linked to the mother’s life.”