Traffic-Related Air Pollution and Ultrasound Parameters of Fetal Growth in Eastern Massachusetts

Abstract

Previous studies have examined the association between prenatal nitrogen dioxide (NO2)-a traffic emissions tracer-and fetal growth based on ultrasound measures. Yet, most have used exposure assessment methods with low temporal resolution, which limits the identification of critical exposure windows given that pregnancy is relatively short. Here, we used NO2 data from an ensemble model linked to residential addresses at birth to fit distributed lag models that estimated the association between NO2 exposure (resolved weekly) and ultrasound biometric parameters in a Massachusetts-based cohort of 9,446 singleton births from 2011-2016. Ultrasound biometric parameters examined included biparietal diameter (BPD), head circumference, femur length, and abdominal circumference. All models adjusted for sociodemographic characteristics, time trends, and temperature. We found that higher NO2 was negatively associated with all ultrasound parameters. The critical window differed depending on the parameter and when it was assessed. For example, for BPD measured after week 31, the critical exposure window appeared to be weeks 15-25; 10-parts-per-billion higher NO2 sustained from conception to the time of measurement was associated with a lower mean z score of -0.11 (95% CI: -0.17, -0.05). Our findings indicate that reducing traffic emissions is one potential avenue to improving fetal and offspring health.

Keywords: air pollution; critical window; fetal growth; nitrogen dioxide; pregnancy; traffic; ultrasound.

Figure 1

The time-varying association between weekly nitrogen dioxide (NO₂) and ultrasound parameters of fetal growth from deliveries at Beth Israel Deaconess Medical Center (n = 9,446), Boston, Massachusetts, 2011–2016. Estimated using distributed lag models adjusted for maternal age, race, education, insurance type, parity, fetal sex, conception year, day of the year of conceptions, area deprivation index, and temperature. Black solid lines show the lag-response estimates, gray shaded areas show the 95% confidence intervals, the horizontal black dashed line indicates the null hypothesis of no effect across all weeks, and vertical black dotted lines indicate the beginning of each trimester. ppb, parts per billion.