Exposure to ambient air pollution and fetal cerebellar transverse diameter: a longitudinal study

Abstract

BACKGROUND AND AIM: Vulnerability to adverse health effects of air pollution begins during the fetal period, as emerging evidence suggests that exposures to fine particulate matter (PM2.5) and nitrogen dioxide (NO2) are associated with low birth weight and prematurity. We aimed to determine the extent to which PM2.5 and NO2 exposures during the preconception period and early pregnancy are associated with cerebellar development as measured by fetal ultrasound. METHODS: Participants were 854 mother-fetal pairs enrolled in the NYU Children’s Health and Environmental Study (CHES) (New York City, 2016-2019). Clinical data on transverse cerebellar diameter (TCD, mm) from ultrasound examinations of pregnant women were extracted from electronic health records. We used a tree-based machine learning method of random forests and gradient boosting machines to predict daily PM2.5 and NO2 at residential addresses. Average PM2.5 and NO2 exposure during three months pre-conception, as well as first and second trimesters were calculated using daily exposure. Associations between each air pollutant and repeatedly measured TCD were examined using linear mixed models adjusted for time of cerebellar measurement, maternal age, pre-pregnancy body mass index, race/ethnicity, employment, education, depressive symptoms, and parity. RESULTS:The mean gestational age was 18.31 weeks (SD=1.91) at the time of first TCD measurement and 24.06 weeks (SD=5.45) at second TCD measurement. Exposures to PM2.5 during the pre-conception period and the first trimester were associated with a smaller TCD (β per µg/m³=-0.15, 95% CI: -0.30, 0.01, and β=-0.30, 95% CI: -0.47, -0.13, respectively). Exposures to NO2 during the pre-conception period and the first trimester were associated with a smaller TCD (β per ppb=-0.05, 95% CI: -0.08, -0.01, and β=-0.05, 95% CI: -0.09, -0.01, respectively). There were no associations between second trimester exposures and TCD. CONCLUSIONS:Exposure to PM2.5 and NO2 during the pre-conception period and early pregnancy may influence fetal brain development. KEYWORDS: Particulate matter, nitrogen dioxide, air pollution, pregnancy, fetal growth, cerebellum