The critical fetal stage for maternal manganese exposure

The geometric mean concentrations of Mn were 2.93 μg/dL, 3.96 μg/dL and 4.41 μg/dL in the first, second and third trimesters, respectively. After adjusting for potential confounders, a consistently negative association was found between maternal Mn levels throughout the three trimesters and birth outcomes. Log-transformed Mn levels in maternal erythrocytes in the second trimester were significantly associated with neonatal birth weight, head and chest circumferences, respectively (β=−556.98 g, p=0.038; β=−1.87 cm, p=0.045; β=−2.74 cm, p=0.024). Despite the limited sample size in the first trimester, negative effects of maternal Mn levels on birth weight (β=−1108.95 g, p<0.01) and chest circumference (β=−4.40 cm, p=0.019) were also observed.