(Reuters Health) - Depression after giving birth is rare among women with no history of psychiatric disorders, but once “postpartum depression” occurs, the odds are much higher that it will happen again after subsequent births, researchers say.

Among more than 450,000 first-time mothers in Denmark with no prior bouts of depression, less than 1 percent had postpartum depression after giving birth. But those who did were 27 to 46 times more likely to experience it again after later births, researchers found.

Overall, about 5 percent to 15 percent of all mothers are diagnosed with depression after giving birth, the study team notes in PLoS Medicine. A history of psychiatric disorders before giving birth increases the risk of postpartum depression significantly.

“The risk of postpartum affective disorder (AD) among women with no previous psychiatric disease is low,” lead study author Marie-Louise Rasmussen told Reuters Health in an email.

But for women who do develop postpartum depression, “the risk of a later affective disorder is increased and the risk of a recurrent postpartum affective disorder episode is relatively high,” said Rasmussen, a researcher with Statens Serum Institut in Copenhagen.

The researchers analyzed data on 457,317 Danish women who had their first babies between 1996 and 2013 and had no history of hospital visits for psychiatric problems or use of antidepressants. During the study, the women had a total of 789,068 births.

Just 0.6 percent of the births were associated with treatment for postpartum depression. The treatment was relatively short in most cases.

Compared to women who didn’t have postpartum depression after their first childbirth, those who did and were treated with antidepressants were 27 times more likely to have postpartum depression after giving birth again. Women hospitalized for a first episode of postpartum depression were 46 times more likely to experience postpartum depression after a subsequent birth.

The findings underline the seriousness of first-time postpartum depression and the need for both primary and secondary preventive measures, Rasmussen said.

“As for all women contemplating to have more children, social support from the spouse and surroundings is very important - probably even more so for women with a previous history of postpartum AD,” she said.

In some women, preventive medication or psychotherapy might be relevant, Rasmussen added.

The report is both reassuring and concerning, said Dr. Jonathan Alpert, chair of the Psychiatry and Behavioral Sciences department at Montefiore Health System in New York, who was not part of the study.

“It is reassuring in finding that for fewer than 1 in 100 women does postpartum depression serious enough to require antidepressant medications and/or hospital admission represent their first psychiatric episode.” It’s also reassuring that the risks are relatively low for women without a prior psychiatric history, he said.

“On the other hand, the report also underscores the importance of postpartum depression as a predictor of future episodes of mood disorder symptoms or postpartum depression.”

Any woman with a psychiatric history should be monitored closely for postpartum depression and any woman with postpartum depression after a first childbirth should be followed closely in later years for risk of depression in general and of postpartum depression after following pregnancies in particular, Alpert said.

“Although postpartum blues or transient moodiness and tearfulness after delivery are common occurrences, persistent depressed mood, severe mood swings, or distorted thinking are signs of needing help right away,” he said.

Women should contact their obstetrician right away for an evaluation and possible treatment such as antidepressants or psychotherapy Alpert said. “Any woman who has thoughts of harming herself or her baby should seek emergency help immediately.”

Reliable sources of online information about postpartum depression and related topics such as risks of antidepressants during pregnancy include postpartum.net, sponsored by Postpartum Support International, and womensmentalhealth.org, sponsored by the MGH Center for Women’s Mental Health, Alpert said.

SOURCE: bit.ly/2fTqK47 PLoS Medicine, online September 26, 2017.