Critical windows of fetal lead exposure: adverse impacts on length of gestation and risk of premature delivery

Abstract

Objective: Research on the role of environmental lead exposure in the complex etiology of premature birth has yielded inconsistent results. We assessed the trimester-specific effect of prenatal lead exposure on gestational age and risk of premature delivery.

Methods: We used linear and logistic regression to identify critical windows of susceptibility to lead exposure on gestational length.

Results: In single-trimester models, decreases in gestational length were most strongly associated with first and second trimester blood lead. In adjusted logistic regression models, a one-standard deviation increase in second trimester blood lead was associated with an odds ratio of prematurity of 1.75 (95% CI: 1.02, 3.02).

Conclusions: Maternal whole blood lead levels measured during first and second trimesters yielded the most prominent inverse association with length of gestation and increased the risk of prematurity.

Figure 1

Linear Regression Plots of Gestational Age vs. Trimester Specific Levels of Blood Lead, Mexico City, Mexico, 1997-1999. Graphs were constructed using the residuals of gestational age controlling for covariates of interest (sex, maternal age, maternal education, history of adverse birth outcome, cigarette smoking, and parity) for the Y Axis and the residuals of the trimester specific blood lead levels controlling for the same covariates of interest. Solid Line=Trimester 1 Blood/Plasma Lead; Dashed Line=Trimester 2 Blood/Plasma Lead; Dotted Line=Trimester 3 Blood/Plasma Lead.

Figure 2

Logistic Regression Analysis of Trimester-Specific Biomarkers of Lead Exposure, Cord Blood Lead, and Odds of Delivering Prematurely, Mexico City, Mexico, 1997-1999. Dots indicate the mean and 95%CI for the odds ratios of delivering prematurely in relation to the trimester-specific biomarkers of lead exposure and cord blood lead.