Association of Fine Particulate Matter and Its Components with Macrosomia: A Nationwide Birth Cohort Study of 336 Chinese Cities

To examine the associations between macrosomia risk and exposure to fine particulate matter (PM_2.5) and its chemical components during pregnancy, we collected birth records between 2010 and 2015 in mainland China from the National Free Preconception Health Examination Project and used satellite-based models to estimate concentrations of PM_2.5 mass and five main components, namely, black carbon (BC), organic carbon (OC), nitrate (NO₃^–), sulfate (SO₄^2–), and ammonium (NH₄⁺). Associations between macrosomia risk and prenatal exposure to PM_2.5 were examined by logistic regression analysis, and the sensitive subgroups were explored by stratified analyses. Of the 3,248,263 singleton newborns from 336 cities, 165,119 (5.1%) had macrosomia. Each interquartile range increase in concentration of PM_2.5 during the entire pregnancy was associated with increased risk of macrosomia (odds ratio (OR) = 1.18; 95% confidence interval (CI), 1.17–1.20). Among specific components, the largest effect estimates were found on NO₃^– (OR = 1.36; 95% CI, 1.35–1.38) followed by OC (OR = 1.23; 95% CI, 1.22–1.24), NH₄⁺ (OR = 1.22; 95% CI, 1.21–1.23), and BC (OR = 1.21; 95% CI, 1.20–1.22). We also that found boys, women with a normal or lower prepregnancy body mass index, and women with irregular or no folic acid supplementation experienced higher risk of macrosomia associated with PM_2.5 exposure.