Blood manganese levels during pregnancy and postpartum depression : A cohort study among women in Mexico

Background: Occupational studies have shown an association between elevated Mn exposure and depressive symptoms. Blood Mn (BMn) naturally rises during pregnancy due to mobilization from tissues, suggesting it could contribute to pregnancy and postpartum depressive symptoms. Objectives: To assess the association between BMn levels during pregnancy and postpartum depression (PPD), creating opportunities for possible future interventions. Methods: We studied 561 women from the reproductive longitudinal Programming Research in Obesity, Growth, Environment, and Social Stressors (PROGRESS) cohort in Mexico City. BMn was measured at the 2nd and 3rd trimesters, as well as delivery. The Edinburgh Postnatal Depression Scale (EPDS) was used to assess PPD symptoms at 12-months postpartum. We used a generalized linear model assuming a Poisson distribution to assess the association between BMn levels and PPD, with adjustments for age, stress and depressive symptoms during pregnancy, education, socioeconomic status, and contemporaneous blood lead levels. Results: The mean +/- standard deviation (SD) EPDS score at 12-months postpartum was 6.51 +/- 5.65, and 17.11% of women met the criteria for possible PPD (score >= 13). In adjusted models, BMn during the 3rd trimester (beta: 0.13, 95% CI: 0.04-0.21) and BMn levels averaged at the 2nd and 3rd trimester (beta: 0.14, 95% CI: 0.02-0.26) had a positive association with EPDS scores at 12 months postpartum. BMn at the 2nd trimester (beta: 0.07, 95% CI: -0.09-0.22) and delivery (beta: 0.03, 95% CI: -0.04-0.10) had a non-significant positive association with EPDS scores at 12-months postpartum. Stress and depressive symptoms during pregnancy was associated with higher EPDS scores at 12-months postpartum in all of the adjusted models but were only significant when either BMn during 3rd trimester or BMn averaged across 2nd and 3rd trimester was assessed as the exposure. Discussion: Our results demonstrate that elevated BMn levels during p