Proximity to roadways and pregnancy outcomes.

Adverse birth outcomes are associated with exposure to air pollution during pregnancy. Road proximity is a simple, widely available metric for capturing local variation in exposure to traffic-related air pollution. We characterized maternal exposure to traffic-related air pollution during pregnancy using residential proximity to major roadways among 2004-2008 singleton births in NC. Controlling for maternal race, age, education, nativity, marital status, and tobacco use, and season of birth, parity, infant sex, and Census tract-level urbanization and income, we evaluated the association between road proximity and pregnancy outcomes using generalized linear mixed models with a random intercept for each Census tract. Birth weight, birth weight percentile for gestational age, gestational hypertension, and small-for-gestational age were not associated with road proximity; however, women residing within 250 m of a major roadway were at 3-5% increased odds of low birth weight, preterm birth, and late preterm birth compared with women residing beyond 250 m (P<0.05). Our analyses demonstrate an association between proximity to major roadways and pregnancy outcomes using a large sample. Road proximity may represent a relatively straightforward method for assessing maternal risk from exposure to traffic-related air pollution, with results offering guidance for studies that can more accurately characterize air pollution exposures.