Women who have complications in pregnancy or a difficult labor stand a much greater chance of having post-natal depression than those who do not, according to experts.

One complication raises the chance of depression but this increases even further if more than one thing goes wrong.

The findings come from analysis of data from almost 5,000 women by Dutch researchers.

They found that women admitted to hospital during their pregnancy had more than twice the risk of post-natal depression as those who stayed out of hospital until delivery time.

Meanwhile, women with pre-eclampsia (linked to high blood pressure) were also more than twice as likely to suffer, the researchers found.

Having an emergency Caesarean section increased the risk 1.5 times, similar to the risk if a baby were admitted to hospital after birth or if there were concerns during labour that the baby was in distress.

One complication meant women were more than twice as likely to get post-natal depression overall, rising to more than five times for women who had four or five complications.

Post-natal depression occurs most often in the first three months after delivery and can range from mild symptoms - sometimes called the "baby blues" - to clinically diagnosed post-natal depression.

Women who are not diagnosed early enough can end up suffering for many months or even years.

"Healthcare practitioners involved in the care for pregnant or postpartum women and their babies should be aware of the substantially increased risk of postpartum depression associated with complicated pregnancies and difficult deliveries," said the report's co-author Pauline Jansen.

"This increased awareness might contribute to quicker diagnosis of postpartum depression."

"The detection and treatment of postnatal depression is an essential part of caring for new mothers and their babies," said Professor Philip Steer, BJOG editor-in-chief.

"It is important that health care professionals are aware of the link between complications and postnatal depression and work together to detect depressive symptoms in women.

"Few studies before this have looked at this area and further research is needed to build on these findings."