Vitamin D Deficiency During Pregnancy Is Associated with Postpartum Depression: A Cohort Study in Southern Brazil.

BACKGROUND/OBJECTIVES: Postpartum depression (PPD) represents a major public health issue, with a direct impact on the quality of life of the mother-infant dyad. 25-hydroxyvitamin D (25(OH)D), hereafter referred to as VitD, has been suggested to exert protective effects on mood regulation. However, current findings remain inconsistent. This study aimed to assess the association between gestational VitD deficiency (≤19.9 µg/mL) and the diagnosis of PPD three months after delivery. METHODS: This longitudinal study followed mother-child dyads in the city of Pelotas, RS, Brazil. A total of 983 pregnant women were initially recruited, of whom 713 had complete data available for this analysis. Blood samples were collected up to 24 weeks of gestation for subsequent measurement of serum VitD levels using chemiluminescence, and PPD diagnosis was established using the Mini International Neuropsychiatric Interview (M.I.N.I. Plus). Logistic regression models were applied and adjusted for potential confounders, such as maternal age, socioeconomic status, and history of depression during pregnancy. RESULTS: In the adjusted model, deficient serum VitD levels were associated with a two-fold-higher likelihood of PPD diagnosis compared to insufficient/sufficient VitD levels (≥20 µg/mL) (OR = 2.0; 95% CI 1.0-4.2; p = 0.049). CONCLUSIONS: These findings highlight the potential role of VitD in maternal mental health and support the importance of monitoring VitD status during pregnancy. From a public health standpoint, ensuring adequate vitamin D levels in prenatal care may contribute to reducing the burden of postpartum depression.