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.