Associations between prenatal exposure to ambient air pollutants and preterm birth in the Atlanta African American maternal-child cohort.

BACKGROUND: Substantial differences in preterm birth (PTB) persist across populations, with African Americans facing the highest rate. While air pollution contributes to PTB, its role in these uneven health burdens remains poorly understood. Studies of PTB subtypes might uncover racial variation in etiology, yet the impact of air pollution is largely understudied. We assessed the associations of prenatal exposures to ambient fine particulate matters (PM2.5), carbon monoxide (CO), and nitrogen oxides (NOx) with PTB and its subtypes using data from the Atlanta African American Maternal-Child Cohort. METHODS: We conducted a prospective analysis among 567 African Americans with singleton pregnancies and without chronic medical conditions. Live births were divided into three categories: PTB, early term birth (ETB), and full-term birth, and PTB was further classified into: spontaneous (i.e., sPTB) and medically indicated (i.e., miPTB). Additionally, a composite category combining PTB and ETB was analyzed. We estimated residential air pollution exposures during five critical windows: 1 month prior to conception, entire pregnancy, the 1st, 2nd, and 3rd trimesters. We performed logistic models and discrete-time survival models for individual air pollutants and quantile g-computation models to evaluate the overall effect, with adjustment of selected covariates. We further evaluated whether infant sex modified the associations between gestational air pollution exposure and PTB risk. RESULTS: PM2.5 exposure during the 1st trimester showed a non-significant trend toward increased PTB risk (OR: 1.50, 95% CI: 0.96–2.35). PM2.5 exposure showed significant associations with miPTB during the 2nd trimester (OR: 1.90, 95%CI: 1.03–3.43). Air pollution mixture models showed similar trends, particularly for miPTB. Also, PM2.5 exposure had stronger effects on early birth (PETB, PTB + ETB), with the largest effect observed across the entire pregnancy (OR: 1.44, 95%CI: 0.90–2.10). Air pollution mixture was significantly associated with increased odds of PETB (OR: 1.33, 95%CI: 1.03–1.72) during the 2nd trimester. We found no evidence that the associations between air pollution exposure and PTB differed by infant sex. DISCUSSION: Our findings suggested that prenatal air pollution exposure, particularly to PM2.5 during early gestational periods, could elevate miPTB risk and early birth among African Americans.