Mothers who have suffered with postnatal depression are unlikely to have more than two children, a new study suggests.

Postnatal depression generally manifests during the first year after a baby is born and symptoms can include low moods, anxiety, frequent crying for no reason, feelings of sadness and loneliness, a lack of energy and feeling unable to cope.

Few studies have assessed the impact of postnatal depression on a woman's future fertility, so UK researchers decided to look into this further.

They studied data on the complete reproductive history of more than 300 women, most of whom were from industrialised countries.

The study found that women who experienced postnatal depression, particularly after the birth of their first child, had lower fertility levels overall.

If a woman suffered high levels of emotional distress after having her first child, this did not appear to affect her decision to have a second child, but it did appear to reduce the likelihood that she would have a third child.

Furthermore, if a woman suffered postnatal depression after both her first and second child, she was much less likely to have a third child. The likelihood was as low as if she had experienced major birth complications.

Around 13% of women in industrialised countries are estimated to develop postnatal depression.

Details of these findings are published in the journal, Evolution, Medicine and Public Health.