Adverse effects of maternal lead levels on birth outcomes in the ALSPAC study: a prospective birth cohort study

Objective
To study the associations of prenatal blood lead levels (B-Pb) with pregnancy outcomes in a large cohort of mother–child pairs in the UK.

Design
Prospective birth cohort study.

Setting
Avon area of Bristol, UK.

Population
Pregnant women enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC).

Methods
Whole blood samples were collected and analysed by inductively coupled plasma dynamic reaction cell mass spectrometry (n = 4285). Data collected on the infants included anthropometric variables and gestational age at delivery. Linear
regression models for continuous outcomes and logistic regression models for categorical outcomes were adjusted for covariates including maternal height, smoking, parity, sex of the baby and gestational age.

Main outcome measures
Birthweight, head circumference and crown–heel length, preterm delivery and low birthweight.

Results
The mean blood lead level (B-Pb) was 3.67 1.47 lg/dl. B-Pb ≥ 5 lg/dl significantly increased the risk of preterm delivery (adjusted odds ratio [OR] 1.94, 95% confidence interval [95% CI] 0.27–2.94) but not of having a low birthweight baby (adjusted OR 1.37, 95% CI 0.86–2.18) in multivariable binary logistic models. Increasing B-Pb was significantly associated with reductions in birth weight (b 13.23, 95% CI 23.75 to 2.70), head circumference (b 0.04, 95% CI 0.07 to 0.06) and crown–heel length (b 0.05, 95% CI 0.10 to 0.00) in multivariable linear regression models.

Conclusions
There was evidence for adverse effects of maternal B-Pb on the incidence of preterm delivery, birthweight, head circumference and crown–heel length, but not on the incidence of low birthweight, in this group of women.