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.