Women who have unintended pregnancies are four times more likely to suffer postnatal depression.
New research from the University of North Carolina, has been published in BJOG (An International Journal of Obstetrics and Gynaecology).
The authors suggested healthcare workers should ask women whether or not they intended to fall pregnant to help identify those at risk.
The study found that one year after having their babies, just 3% of women who intended to fall pregnant suffered from postnatal depression compared to 12% of women who had "mistimed" or "unwanted" pregnancies.
The researchers questioned a group of women between 15 and 19 weeks pregnant. Some 433 women described their pregnancies as intended, 207 said the pregnancy was mistimed and 40 (6%) said it was unwanted. Both unwanted and mistimed pregnancies were categorised as unintended.
The study followed up 688 women three months after they gave birth and 550 women after 12 months.
At three months, 11% of women who reported unintended pregnancies were suffering from postnatal depression compared with 5% of women who intended to fall pregnant. The figure after a year was 12% for unintended pregnancies and 3% for intended pregnancies.
Women with an unintended pregnancy were still twice as likely to have postnatal depression at 12 months when age, education and poverty status was taken into account.
Dr Rebecca Mercier, co-author of the study, acknowledged that many elements contribute to postnatal depression. But she said the results showed unintended pregnancy resulting in live birth could also be a contributing factor and therefore unintended pregnancy carried to term may have a long-term effect.
She recommended that healthcare professionals should therefore consider asking about pregnancy at early antenatal visits to screen for unintended pregnancy as screening interventions to identify women at risk could allow targeted intervention when appropriate .
Copyright Press Association 2013