Prenatal exposure to ambient air pollution and traffic and indicators of adiposity in early childhood: the Healthy Start study

Background: Prenatal exposure to ambient air pollution and traffic have been related to a lower birth weight and may be associated with greater adiposity in childhood. We aimed to examine associations of maternal exposure to ambient air pollution and traffic during pregnancy with indicators of adiposity in early childhood. Methods: We included 738 participants of the Colorado-based Healthy Start study whose height, weight, waist circumference and/or fat mass were measured at age 4–6 years. We estimated residential exposure to ambient concentrations of fine particulate matter (PM_2.5) and ozone (O₃) averaged by trimester and throughout pregnancy via inverse distance-weighted interpolation of central site monitoring data. We assessed the distance to the nearest major roadway and traffic density in multiple buffers surrounding the participants’ homes. Associations of prenatal exposure to air pollution and traffic with overweight, waist circumference, percent fat mass and fat mass index (FMI) were assessed by logistic and linear regression. Results: Associations of exposure to PM_2.5 and O₃ at the residential address during pregnancy with percent fat mass and FMI at age 4–6 years were inconsistent across trimesters. For example, second trimester PM_2.5 was associated with a higher percent fat mass (adjusted difference 0.70% [95% CI 0.05, 1.35%] per interquartile range (IQR; 1.3 µg/m³) increase), while third trimester PM_2.5 was associated with a lower percent fat mass (adjusted difference −1.17% [95% CI −1.84, −0.50%] per IQR (1.3 µg/m³) increase). Residential proximity to a highway during pregnancy was associated with higher odds of being overweight at age 4–6 years. We observed no associations of prenatal exposure to PM_2.5 and O₃ with overweight and waist circumference. Conclusions: We found limited evidence of associations of prenatal exposure to ambient PM_2.5 and O₃ with indicators of adiposity at age 4–6 years. Suggestive relationships between residential proximity to a highway during pregnancy and greater adiposity merit further investigation.