Women with high and low body mass index in the first trimester of their first pregnancies are at an increased risk of developing postpartum depression, a population-based study of more than 600,000 new mothers shows.
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“Our findings show a U-shaped association between BMI extremes and clinically significant depression after childbirth,” Michael E. Silverman, PhD, and his associates reported in the Journal of Affective Disorders. “Specifically, women in the lowest and highest groups were at a significantly increased risk for developing [postpartum depression].”
Dr. Silverman and his associates used the Swedish Medical Birth Register to identify women who delivered first live singleton infants from 1997 to 2008. They then calculated the risk of postpartum depression in relation to each woman’s BMI and history of depression. Postpartum depression was defined as a clinical depression diagnosis within 1 year after delivery, Dr. Silverman and his associates wrote.
The investigators found that women with low BMI (less than 18.5 kg/m2) were at an increased postpartum depression risk (relative risk [RR], 1.52; 95% confidence interval, 1.30-1.78), as were those with high BMI (greater than 35 kg/m2) (RR, 1.23; 95% CI, 1.04-1.45).
In addition, an important difference was found between women with low and high BMI.
“Women in the highest BMI group were only at an increased risk for [postpartum depression] if they had no history of depression, showing for the first time how [postpartum depression] risk factors associated with BMI are modified by maternal depression history,” said Dr. Silverman of the department of psychiatry at the Icahn School of Medicine at Mount Sinai, New York, and his associates.
The investigators cited several limitations. For example, only first births were analyzed, which suggests that the incidence of postpartum depression might have been underestimated. Another limitation is that the registry might not have captured women with mild depression. Nevertheless, they said, the study has important implications.
“ Because pregnant women represent a medically captured population,” they wrote, the findings support implementing preventive strategies for postpartum depression and health literacy for high-risk women.
Dr. Silverman and his associates reported having no conflicts of interest. The study was supported by a grant from the National Institutes of Health.
SOURCE: Silverman ME et al. J Affect Disord. 2018 Nov;240:193-8.