The Effect of Ambient Air Pollution during Early Pregnancy on Fetal Ultrasonic Measurements during Mid-Pregnancy

BACKGROUND Over the past decade there has been mounting evidence that ambient air pollution during pregnancy influences fetal growth. OBJECTIVES This study was designed to examine possible associations between fetal ultrasonic measurements collected from 15,623 scans (13-26 weeks gestation) and ambient air pollution during early pregnancy. METHODS We calculated mothers' average monthly exposures over the first 4 months of pregnancy for the following pollutants: particulate matter < 10 microm aerodynamic diameter (PM10), ozone, nitrogen dioxide, and sulfur dioxide. We examined associations with fetal femur length (FL), biparietal diameter (BPD), head circumference (HC), and abdominal circumference (AC). Final analyses included scans from only those women within 2 km of an air pollution monitoring site. We controlled for long-term trend, season, temperature, gestation, mother's age, socioeconomic status, and fetal sex. RESULTS A reduction in fetal AC was associated with O3 during days 31-60 [-1.42 mm; 95% confidence interval (CI), -2.74 to -0.09], SO2 during days 61-90 (-1.67 mm; 95% CI, -2.94 to -0.40), and PM10 during days 91-120 (-0.78 mm; 95% CI, -1.49 to -0.08). Other results showed a reduction in BPD (-0.68 mm; 95% CI, -1.09 to -0.27) associated with SO2 during days 0-30, a reduction in HC (-1.02 mm; 95% CI, -1.78 to -0.26) associated with PM10 during days 91-120, and a reduction in FL associated with PM10 during days 0-30 (-0.28 mm; 95% CI, -0.48 to -0.08) and 91-120 (-0.23; 95% CI, -0.42 to -0.04). CONCLUSION We found strong effects of ambient air pollution on ultrasound measures. Future research, including more individually detailed data, is needed to confirm our results.