Prenatal lead and intelligence quotient measured in children and adolescents: A systematic review and meta-analysis

Lead is a well-recognized neurotoxic metal with demonstrated consistent detrimental effects on children's intelligence quotient (IQ) in the postnatal period. However, there is no such consensus about the effects of prenatal exposures.

We aimed to examine the effect of prenatal lead exposure on children's intelligence quotient.

We conducted a systematic review with meta-analysis based on three databases: PubMed (MEDLINE), Web of Science, and Lilacs (Latin American and Caribbean Health Sciences Literature). We included studies where exposure involved biomarkers of lead exposure (e.g., blood, urine, etc.) during the prenatal period, and global IQ assessments were conducted in children aged 5 years or older. We standardized the estimates to linear point estimates. The Risk of Bias (RoB) in Non-randomized Studies of Exposures (ROBINS-E) tool was used to evaluate potential systematic errors. We analyzed the pooled estimates using random effects models, also considering fixed effects models. Pooled effects were examined separately by sex. To assess heterogeneity across studies, we employed the I² statistic and Cochran's Q test.

Only 7 studies were included in analyses. In those studies evaluating blood lead levels, we found a modest negative association between prenatal Pb and standardized IQ scores, although the confidence interval included the null value (β: -0.06; 95%CI: -0.17, 0.05; I²: 24.1%).

Results from our study suggest that prenatal lead exposure may be associated with modestly lower intelligence quotient scores in children 5 years and older. However, research is sparse and more studies are needed to investigate confounding factors and whether the effect varies by sex.