State-wide birth cohort study of ozone and fetal growth by socioeconomic status and urbanicity

Findings for the association between ozone and fetal growth have been inconsistent in the literature. The objective of this study was to assess whether ozone concentration during pregnancy is associated with risk of low birth weight (LBW) and small for gestational age (SGA) infants. Further, this study will examine whether the potential associations vary by socioeconomic status (SES) or urban-rural differences. LBW and SGA were determined using birth certificates from North Carolina (2002-2005). Ambient ozone concentrations were calculated using a Bayesian hierachical model of air pollution generated by “fusing” modeled air pollution predictions with measured air monitor data. SES was estimated using maternal Medicaid use as recorded on birth records. Urbanicity was based on geocoded address and county-level rural-urban continuum codes. Binomial regression was performed and stratified analyses examined associations within categories of SES and urbanicity. Ozone concentration was positively associated with SGA and LBW [risk ratios for an increase equal to the interquartile range in ozone during the third trimester: 1.09 (95% CI 1.06, 1.13) for SGA and 1.28 (95% CI 1.19, 1.37) for LBW]. These associations were similar across categories of Medicaid use and urbanicity. In summary, we examined SGA and LBW for all births in North Carolina from 2002-2005 using air pollution data that covers urban and rural areas and observed that ozone concentration during pregnancy affects fetal growth risk. This association did not vary by SES or urbanicity. Disclaimer: The views expressed are those of the authors and do not necessarily reflect the views or policies of the US EPA.