Hydroxylated polychlorinated biphenyl metabolites (OH-PCBs), maternal smoking and size at birth

•Among pregnant women who smoked, high levels of 4-OH-CB107, a metabolite of PCB118, was associated with a reduction in birth weight of 316 (95% confidence interval 566, 65) grams. The association was not present for non-smoking mothers.•Among pregnant women who smoked PCB118 was associated with increases in birth weight.•These associations were not mediated by maternal thyroid status.•These results may provide insight into the mechanisms underlying associations between halogenated endocrine disruptors and pregnancy outcomes.

In a sample of 442 births from the Child Health and Development Studies cohort, we examined associations between maternal prenatal exposure to hydroxylated polychlorinated biphenyl metabolites (OH-PCBs) and pregnancy outcomes, and whether associations were mediated by maternal thyroid hormone levels and/or modified by maternal smoking. Compared to nonsmokers, smokers had twice the mean concentration of 4-OH-CB107 (p < 0.001) and lower levels of its parent compound, PCB118 (p = 0.001). Among mothers who smoked, the birth weight of newborns with maternal concentrations of 4-OH-CB107 in the upper quartile was 316 g lighter (95% confidence interval (CI) 566, 65) compared to those with maternal concentrations in the lowest quartile, after control for PCB118 and other potential confounders. This association was not observed for non-smoking mothers and was not mediated by maternal thyroid hormone levels. Maternal prenatal 4-OH-CB107 levels appear to be influenced by maternal smoking and contribute to lower birth weight among smokers.