Associations between urinary polycyclic aromatic hydrocarbon biomarker concentrations and birth outcomes in the LIFECODES cohort.

Environmental exposure to polycyclic aromatic hydrocarbons (PAH) is ubiquitous and may impact fetal development leading to adverse birth outcomes. PAHs result from incomplete combustion and exposure sources include inhalation of cigarette smoke and car exhaust, ingestion of charred meat, and many others. The purpose of this study was to determine associations between prenatal PAH biomarker concentrations and birth outcomes. Our nested case-control study included 123 preterm birth cases and 335 term controls from the LIFECODES cohort between 2006 and 2008 (n = 458). Eight urinary PAH metabolites were measured in urine samples collected at up to four study visits (median 12, 18, 24, 34 weeks gestation). Linear and logistic regression were used to model gestational geometric mean PAH biomarker concentrations in relation to preterm birth, birth weight z-score, and small or large for gestational age with adjustment for potential confounders. Effect modification by infant sex was also explored. Odds ratios for preterm birth were elevated for most PAH metabolites but confidence intervals included the null. For most PAH metabolites, a significant inverse association was observed for birth weight for gestational age z-score, and a corresponding increase in the odds of small for gestational age (SGA). For example, an interquartile range increase in 2-hydroxynapthalene (2-NAP) was associated with a significantly lower birth weight z-score (β: 0.22; 95 % CI: 0.36, -0.08) and 1.90 times the odds of SGA (95 %CI: 1.41, 2.55). Further study should aim to determine the extent and mechanisms by which PAH exposure impacts fetal growth.