Mental disorders in motherhood according to prepregnancy BMI and pregnancy-related weight changes-A Danish cohort study

- Incidence of depression/anxiety up till 6 years postpartum was 6.1% in new mothers.
- Being underweight before pregnancy increased the risk of these mental disorders.
- No increased risk was observed in obese women after adjustment for confounders.
- Both postpartum weight retention and loss 6 months after birth increased the risk.
- Postpartum weight changes were associated with increased risk in all BMI groups.

BackgroundPrevious studies have shown an association between prepregnancy BMI and postpartum depression, but little is known about this association beyond one year postpartum and the influence of postpartum weight retention (PPWR).MethodsWe used data from 70 355 mothers from the Danish National Birth Cohort to estimate the associations between maternal prepregnancy BMI and PPWR, respectively, and incident depression/anxiety disorders until six years postpartum. Outcome was depression or anxiety diagnosed clinically or filling a prescription for an antidepressant. Cox regression was used to estimate hazard ratios (HR) with 95% confidence intervals (CI). Follow-up started at the day of delivery. For the analysis regarding PPWR, follow-up started six months postpartum.ResultsUnderweight, overweight and obesity were associated with depression and/or anxiety disorders when compared to normal-weight, though the associations were attenuated after adjustments (HR 1.24 [95% CI 1.06-1.45], 1.05 [95% CI 0.96-1.15] and 1.07 [95% CI 0.95-1.21] for underweight, overweight and obese, respectively).Compared to mothers who had returned to their prepregnancy BMI, risk of depression/anxiety disorders was increased for mothers, who from prepregnancy to 6 months postpartum experienced either weight loss >1 BMI unit (HR 1.19 [95% CI 1.06-1.25]), weight gain of 2-3 BMI units (HR 1.23 [95% CI 1.08-1.40]), or weight gain of ≥3 BMI units (HR 1.21 [95% CI 1.05-1.40]).LimitationCausal direction and mechanisms behind the associations are largely unknown.ConclusionsLow prepregnancy body weight and postpartum weight gain or loss are associated with occurrence of depression and anxiety disorders.