Measuring levels of a hormone midway through pregnancy may predict a woman's risk of postnatal depression.
Postnatal depression generally starts within four to six weeks of giving birth and affects 10-15% of mothers.
Known risk factors for PND include a history of depression, stressful life events, a lack of social support, low self-esteem, anxiety or stress during pregnancy.
In a study of 100 women, levels of the pCRH hormone (placental corticotropin-releasing hormone) at 25 weeks helped predict three-quarters of those who developed the so-called baby blues. The test could be used routinely to screen for depression according to the US researchers.
Other studies have also looked at the effects of hormones during pregnancy although this is the first study to specifically measure the relationship with depression and pCRH .
The researchers found that levels of pCRH when the women were 25 weeks pregnant strongly predicted future development of depression. It was more accurate when depressive symptoms in the middle of pregnancy were taken into account.
Levels of the hormone increase during pregnancy which increases the production of cortisol - which helps the body deal with stress. After birth, levels of pCRH drop dramatically leading to a dip in cortisol.
Dr Patrick O'Brien, spokesman for the Royal College of Obstetricians and Gynaecologists, said the results were very interesting but needed to be tested on a bigger sample group.
He said: "The thing with postpartum depression is that once it is identified it usually can be treated very well. But the problem is that often women withdraw within themselves and don't seek help."
February 2009
The findings are published in Archives of General Psychiatry. | 
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