Gestational fine particulate matter exposure and perinatal outcomes in the ECHO cohort: Associations across pregnancy...

Evidence is inconsistent regarding which windows of PM_2.5 exposure are critical for adverse perinatal outcomes. We investigated associations between timing of gestational PM_2.5 exposure and perinatal outcomes. Participants included 19,108 mother-infant dyads from 51 sites of the Environmental influences on Child Health Outcomes (ECHO) cohort. Repeated measures of PM_2.5 exposure were included based on high-resolution spatiotemporal models for trimesters 1-3, early first trimester (≤14 days), and late first trimester (70-92 days). We estimated associations of PM_2.5 exposure (per 5 μg/m³ increase) and continuous outcomes (gestational age at birth [GA] and birthweight for gestational age z-scores [BWZs]) using generalized estimating equation (GEE) models for linear regression. Poisson regression via GEE was used to estimate risk ratios (RRs) of PM_2.5 exposure (per 5 μg/m³ increase) with binary outcomes (preterm birth [PTB], <37 completed weeks of gestation), and term small for gestational age [SGA], <10th percentile). We explored effect modification by participants' characteristics. In fully adjusted models, early 1st trimester PM_2.5 exposure was associated with lower BWZ (β = -0.03, 95 % CI -0.06, -0.001); association with term SGA was RR = 1.06, 95 % CI 0.99, 1.13. Results were mostly null for other windows of gestational exposure. When stratified by sex, early pregnancy PM_2.5 exposure and lower BWZ associations were observed among females, but not males. Suggestive evidence indicates that associations of PM_2.5 exposure with GA, PTB risk, and term SGA risk may vary by maternal race and ethnicity. Our results suggest that policies and practices that reduce the risks of PM_2.5 exposure, particularly in pre-conception and early pregnancy, may improve perinatal outcomes.