Prenatal lead exposure modifies the association of maternal self-esteem with child adaptive ability.

Background: A child's adaptive ability is important for personal career and social development. Maternal self-esteem may help shape a child's behavior. This study aims to investigate whether maternal self-esteem measured when their children were toddlers predicts their children's adaptive skills at school age, and whether prenatal lead exposure modifies such a relationship.
Methods: We assessed prenatal lead exposure using cord blood lead and maternal bone lead around delivery (tibia and patella lead measured in vivo by K-x-ray-fluorescence) among 192 mother-child pairs investigated in Mexico from 1994 to 2011. Maternal self-esteem was measured using the Coopersmith-Self-esteem-Inventory when children were 2 years old. When children were 7-to-15 years old, we measured children's blood lead levels and administered the 2nd edition of Behavior-Assessment-System-for-Children (BASC-2) parent-rating-scales (PRS) and Self-Reports of Personality (SRP) to evaluate children's adaptive skills.
Results: Median (P25, P75) values for maternal patella and tibia lead, cord blood lead and children's current blood lead levels were 12.6 (3.2, 21.7) μg/g, 10.2 (4.1, 16.0) μg/g, 5.5 (3.5, 8.1) μg/dL and 2.7 (2.0, 4.0) μg/dL, respectively. In adjusted models, increased maternal self-esteem was associated with increased adaptive T-scores on the BASC-2 PRS and SRP scales. This relationship was weaker in high prenatal lead-exposure groups (high cord blood lead or patella lead groups, P25P100) compared with low prenatal lead-exposure (low cord blood lead or patella lead groups, P1P25) groups (P-interaction values < 0.10). No significant interactions between maternal tibia lead and self-esteem on children's adaptive T-scores were observed (P-interaction values > 0.10).
Conclusions: Toddlers of mothers with high (vs. low) self-esteem have better adaptive abilities when they are of school-age. Prenatal lead exposure may attenuate or eliminate this positive association.
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