Postpartum psychiatric risk varies with birth order
medwireNews: The elevated postpartum risk for a first-time psychiatric episode, particularly of bipolar disorder, is most marked after a first delivery, shows a population-based study.
Women were at increased risk for needing inpatient psychiatric care for a range of conditions after their first delivery, report Trine Munk-Olsen (Aarhus University, Denmark) and co-workers.
But after their second delivery, the increased risk was confined to unipolar depression and adjustment disorders.
“It is possible that the effect of primiparity results from biological differences between first and subsequent pregnancies,” the researchers write in Bipolar Disorders. “An alternative explanation for the observed risk in first-time mothers is that the psychological stress of motherhood is most prominent after the first birth.”
However, they note that the impact of a first delivery was most marked for bipolar disorder, at an incidence rate ratio (IRR) of 10.53 per 1000 person–years during the first 59 days after delivery, whereas the IRRs for schizophrenia, unipolar depression, and adjustment disorders were 3.81, 3.39, and 3.11 per 1000 person–years, respectively.
This difference in effect size favoring bipolar rather than unipolar disorders “may not be consistent with a purely psychosocial explanation,” comments the team, adding that “[t]here is considerable evidence pointing to childbirth being a specific risk factor for bipolar disorder.”
The study included 750,127 Danish women who had at least one delivery between 1970 and 2010, of whom 2300 required postpartum in-hospital psychiatric treatment.
The risk for unipolar depression and adjustment disorders persisted longer after delivery than that for other disorders, at up to 179 and 119 days, respectively, and these were the only disorders to have significantly increased IRRs after a second delivery.
However, the risk for any psychiatric disorder after a second delivery varied according to the length of time since the first delivery. The longer the interval between deliveries, the greater the chances for women having a psychiatric episode, rising to an IRR of about 3.5 for a gap of 6 years or more.
“We speculate that biological differences between first and subsequent pregnancies diminish with increasing inter-pregnancy intervals, and that this results in the increased risk of postpartum psychiatric disorders after the second childbirth with increasing pregnancy intervals,” say the researchers.
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Eleanor McDermid, Senior medwireNews Reporter