Air pollution exposure during pregnancy and ultrasound and birth measures of fetal growth: A prospective cohort study in Korea.

Few studies have examined the effects of air pollution on fetal growth based on ultrasound measures during pregnancy. More data is needed to evaluate the windows of special vulnerability. Our aim was to investigate the association of ambient air pollution during pregnancy with fetal and neonatal characteristics in a cohort of Korean women. Maternal exposure to particulate matter with an aerodynamic diameter<10μm (PM10) and nitrogen dioxide (NO2) was estimated using land-use regression models based on residential address. The biparietal diameter (BPD), abdominal circumference (AC), femur length (FL), and estimated fetal weight (EFW) were evaluated via ultrasonography, and birth weight (BW), birth length (BL), and head circumference at birth (BHC) were obtained from medical records. The multiple linear regression model was used to adjust for confounders, and the mixed-effect model was used to evaluate longitudinal effect. The negative effects for NO2 and PM10 were estimated; in the adjusted analyses the decreases of BPD were -0.26mm (95% confidence interval [CI]=-0.41 to -0.11, with a 10μg/m3 increase) in the second trimester for NO2, and -0.30mm (95% CI=-0.59 to -0.03, with a 10μg/m3 increase) in the third trimester for PM10. Both NO2 and PM10 levels (10μg/m3) during third trimester were inversely associated with BHC, and NO2 level was inversely associated with BL in all exposure windows. No significant associations for AC, FL, and EFW were observed. The longitudinal analyses showed inverse association of NO2 exposure with head and length growth (P<0.001). Our findings suggest that ambient air pollution is associated with impaired fetal head size from mid-gestation onwards.