Fetal Lead Exposure at Each Stage of Pregnancy as a Predictor of Infant Mental Development

TLDR

Prenatal lead exposure’s impact on neurodevelopment is unclear regarding consistency, trimester vulnerability, and optimal exposure estimation. The study aimed to assess how prenatal lead exposure affects infant neurodevelopment by repeatedly measuring maternal plasma and whole blood lead levels across trimesters. Researchers measured maternal plasma and whole blood lead each trimester in 146 Mexican women, collected cord blood at delivery, assessed child blood lead at 12 and 24 months, administered Bayley Scales, and performed multivariate regression adjusting for covariates. First‑trimester maternal lead, especially plasma, significantly predicted lower Mental Development Index scores—each 1‑SD increase in plasma lead reduced MDI by 3.5 points—while later trimesters and postnatal lead had weaker associations.

Abstract

BackgroundThe impact of prenatal lead exposure on neurodevelopment remains unclear in terms of consistency, the trimester of greatest vulnerability, and the best method for estimating fetal lead exposure.ObjectiveWe studied prenatal lead exposure's impact on neurodevelopment using repeated measures of fetal dose as reflected by maternal whole blood and plasma lead levels.MethodsWe measured lead in maternal plasma and whole blood during each trimester in 146 pregnant women in Mexico City. We then measured umbilical cord blood lead at delivery and, when offspring were 12 and 24 months of age, measured blood lead and administered the Bayley Scales of Infant Development. We used multivariate regression, adjusting for covariates and 24-month blood lead, to compare the impacts of our pregnancy measures of fetal lead dose.ResultsMaternal lead levels were moderately high with a first-trimester blood lead mean (± SD) value of 7.1 ± 5.1 μg/dL and 14% of values ≥10 μg/dL. Both maternal plasma and whole blood lead during the first trimester (but not in the second or third trimester) were significant predictors (p < 0.05) of poorer Mental Development Index (MDI) scores. In models combining all three trimester measures and using standardized coefficients, the effect of first-trimester maternal plasma lead was somewhat greater than the effect of first-trimester maternal whole blood lead and substantially greater than the effects of second- or third-trimester plasma lead, and values averaged over all three trimesters. A 1-SD change in first-trimester plasma lead was associated with a reduction in MDI score of 3.5 points. Postnatal blood lead levels in the offspring were less strongly correlated with MDI scores.ConclusionsFetal lead exposure has an adverse effect on neurodevelopment, with an effect that may be most pronounced during the first trimester and best captured by measuring lead in either maternal plasma or whole blood.