BackgroundAflatoxin (AF) exposure is associated with child growth faltering in cross-sectional studies, with limited findings from longitudinal studies.ObjectivesTo evaluate the relationship between maternal AF B1-lysine adduct concentration, child AF B1-lysine adduct concentration, and child growth in the first 30 mo of life.MethodsAF B1-lysine adduct was measured in mother-child dyad plasma samples using isotope dilution mass spectrometry. Using linear regression, we assessed the relationship between AF B1-lysine adduct concentration and child weight, height, and head and mid-upper arm circumferences at 1 wk, 6, 12, 18, 24, and 30 mo of age.ResultsIn adjusted models, maternal prenatal AF B1-lysine adduct (pg/μL) was positively associated with newborn anthropometric outcomes; largest beta coefficients for associations between standardized values were for newborn weight-for-agez-score [β = 0.13; 95% confidence interval (CI): 0.02, 0.24;P< 0.05 and β = 0.11; 95% CI: 0.00, 0.22;P< 0.05 for second and third trimester AF, respectively]. Child AF B1-lysine adduct (pg/μL) at 6 mo was negatively associated with head circumference-for-agez-score at 6, 18, 24, and 30 mo, with beta coefficients ranging from β = –0.15; 95% CI: –0.28, –0.02 to β = –0.17; 95% CI: –0.31, –0.03;P< 0.05); 18-mo AF was negatively associated with anthropometric outcomes at 18, 24, and 30 mo, most consistently with length-for-agez-score (β = –0.18; 95% CI: –0.32, –0.04, β = –0.21; 95% CI: –0.35, –0.07, β = –0.18; 95% CI: –0.32, –0.03 at 18, 24 and 30 mo, respectively).ConclusionsChild AF exposure was associated with impaired child growth, but maternal AF exposure was not. Exposure during infancy was linked to persistent deficit in head circumference, implying reduced brain size lasting beyond the age of 2 years. Exposure at 18 mo was linked to persistent linear growth deficit. Further research should elucidate mechanisms through which AF affects child growth.