Maternal blood manganese level and birth weight: a MOCEH birth cohort study

Background: Manganese (Mn) is an essential trace element for humans and animals, but excess intake of Mn can lead to adverse developmental outcome. Few studies have investigated the effects of deficiency or excess of Mn on the human foetus. In this study, we assessed the quantitative relationship between maternal blood Mn and birth weight of a newborn. Methods: We performed analysis on 331 full-term, live birth singleton mother-infant pairs enrolled from July 2007 to December 2009 in the Mother and Children's Environmental Health (MOCEH) study in Korea. A questionnaire on general characteristics, a review of medical records, and maternal whole blood Mn analysis were performed at full-term pregnancy. We evaluated the relationship between maternal blood level of Mn and the birth outcome using logistic regression and generalised additive model. Results: The mean Mn concentration in whole maternal blood was 22.5 mu g/L. We found a curvilinear relationship between maternal blood Mn and birth weight after adjusting for potential confounders. Birth weight peaked at the maternal blood Mn level of 30 and 35 mu g/L. An increased probability of birth weight below 3000 g was observed at both below 16.9 mu g/L (odds ratio = 2.77, 95% CI: 0.89-8.65) and above 26.9 mu g/L of maternal blood Mn level (odds ratio = 2.66, 95% CI: 0.84-8.08). Conclusions: Our study found that both extreme level of maternal Mn level was associated with lower birth weight outcome in a nonlinear fashion.