Background: Previous studies of air pollution and birth outcomes have not evaluated whether complicated pregnancies might be susceptible to the adverse effects of air pollution. We hypothesized that trimester mean pollutant concentrations would be associated with fetal growth restriction, with larger risks among complicated pregnancies.
Methods: We used a multiyear linked birth certificate and maternal/newborn hospital discharge dataset of singleton, term births to mothers residing in New Jersey at the time of birth, who were White (non-Hispanic), African American (non-Hispanic), or Hispanic. We defined very small for gestational age (VSGA) as a fetal growth ratio <0.75, small for gestational age (SGA) as ≥0.75 and <0.85, and 'reference' births as ≥ 0.85. Using polytomous logistic regression, we examined associations between mean pollutant concentrations during the 1st, 2nd, and 3rd trimesters and the risks of SGA/VSGA, as well as effect modification of these associations by several pregnancy complications.
Results: We found significantly increased risk of SGA associated with 1st and 3rd trimester PM2.5, and increased risk of VSGA associated with 1st, 2nd, and 3rd trimester NO2 concentrations. Pregnancies complicated by placental abruption and premature rupture of the membrane had ~2-5 fold greater excess risks of SGA/VSGA than pregnancies not complicated by these conditions, although these estimates were not statistically significant.
Conclusions: These findings suggest that ambient air pollution, perhaps specifically traffic emissions during early and late pregnancy and/or factors associated with residence near a roadway during pregnancy, may affect fetal growth. Further, pregnancy complications may increase susceptibility to these effects in late pregnancy.