Prenatal exposure to manganese at environment relevant level and neonatal neurobehavioral development

•A nonlinear relationship between cord serum Mn and neonatal behavioral neurological assessments (NBNA).•NBNA score decreased with increasing Mn levels after 5.0 μg/L.•A threshold cord serum Mn of 5.0 μg/L existed for lower NBNA.

BackgroundEffects of prenatal Manganese (Mn) exposure at an environmental relevant level on neonatal neurodevelopment remains unclear.ObjectivesIn the multi-center study, we assessed the impact of low level prenatal Mn exposure on neonatal behavioral neurological assessments (NBNA), and explore a threshold umbilical cord blood Mn on neonatal neurological development.MethodsWe investigated 933 mother-newborn pairs in Shanghai, China, from 2008 through 2009. Umbilical cord serum concentrations of Mn were measured and NBNA tests were conducted. The NBNA contains five clusters: behavior, active tone, passive tone, primary reflexes and general assessment with a maximal total score of 40. The score<37 is defined as low.ResultsThe median serum Mn concentration was 4.0 μg/L. Of the 933 infants, 44 (4.7%) had low NBNA. After adjusting for potential confounders, a high level of Mn (≥75th percentile ) was associated with a lower NBNA score (adjusted ß=−1.1, 95% CI: −1.4–0.7, p<0.01) and a higher risk of low NBNA (adjusted OR=9.4, 95% CI: 3.4–25.7, p<0.01). A nonlinear relationship was observed between cord serum Mn and NBNA after adjusting for potential confounders. NBNA score decreased with increasing Mn levels after 5.0 μg/L(LgMn≥0.7). The cord serum Mn≥5.0 μg/L had adverse effects on behavior, active tone and general reactions of clusters (p<0.001).ConclusionsHigh prenatal Mn exposure even at an environmental relevant level, is associated with poor fetal neurobehavioral development in a nonlinear pattern. A threshold cord serum Mn of 5.0 μg/L existed for lower neonatal behavioral neurological assessments.