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.