Gestational hemodilution as a putative risk factor for postpartum depression: A large-scale nationwide longitudinal cohort study

Background: While anemia during pregnancy has been linked to increased postpartum depression (PPD) risk, longitudinal studies on the association between gestational hemodilution, represented by decreased hematocrit (Hct) during the transition from the 1st to 2nd trimester, and PPD risk, are scarce. The current study aimed to investigate this association in a nationwide cohort over the perinatal period. Methods: This retrospective cohort study included 104,715 women who gave birth between January 2008 and December 2015. The cohort was followed up for new-onset PPD during the year post birth and gestational hemodilution was assessed by the change in Hct levels (Δ: 2nd-1st trimester). The cohort was divided into three hemodilution groupings: maximal and minimal 10 % of mothers and intermediate 80 %. Multivariable regression analyses were performed to estimate the association between gestational hemodilution and PPD, adjusting for confounders. Results: Among the full cohort, 2.2 % (n = 2263) met the definition of new-onset PPD. Mothers with greater hemodilution had higher rates of PPD: 2.7 % (n = 269) in the maximal hemodilution group, 2.1 % (n = 1783) in the intermediate and 1.9 % (n = 211) in the minimal hemodilution group (p < 0.001). The maximal hemodilution group had higher rates of pre-gestational psychiatric disorders (p < 0.001) and higher adjusted risk for PPD [OR = 1.18, 95 % CI (1.04, 1.35)]. Limitations: Data on iron levels and supplementation were unavailable, thus it could not be adjusted for in the analysis. Conclusions: Women in the top 10th percentile of gestational hemodilution may be at risk for PPD, justifying monitoring of gestational Hct as a biomarker for PPD.