Maternal low level lead exposure and fetal growth

Background: The exposure of the general population to low lead levels remains a public health concern.

Objective: To examine whether maternal blood lead levels less than 10 ug/dl were associated with decreased fetal growth.

Methods: We linked Heavy Metals Registry blood lead records with birth certificates to identify 44,932 mother-infant pairs in upstate New York in a retrospective cohort study from 2003 through 2005. Logistic regression was used to calculate odds ratios (OR) to adjust for potential confounders.

Results: Compared to maternal blood lead levels less than or equal to 1 ug/dl, maternal blood lead levels between 4.0-9.9 ug/dl were not significantly associated with low birth weight birth, preterm birth, or small for gestational age for all births combined. However, maternal blood lead levels between 4.0-9.9 ug/dl were associated with an approximately 40% higher risk for low birth weight among Caucasian women (OR 1.37, 95% confidence interval (CI): 1.07-1.76). Mothers 30-34 years of age with blood lead levels 4.0-9.9 ug/dl experienced a doubling of risk in very preterm birth (OR 2.11, 95% CI: 1.00-4.47). Mothers with two or more previous live births and blood lead levels 4.0-9.9 ug/dl were at 40% higher risk in delivering small for gestational age babies (OR 1.37, 95% CI: 1.03-1.83).

Conclusion: The findings suggest that low level blood lead levels may be associated with decreased fetal growth among select groups of women such as Caucasians whose baseline risk for these outcomes is otherwise low. Our study supports lead screening during pregnancy especially among Caucasians, women of 30 years of age or more, and women with two or more previous births.