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. It was hypothesised that trimester mean pollutant concentrations could be associated with fetal growth restriction, with larger risks among complicated pregnancies.
Methods: 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 was used. Very small for gestational age (VSGA) was defined 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, associations between mean pollutant concentrations during the first, second and third trimesters and the risks of SGA/VSGA were examined, as well as effect modification of these associations by several pregnancy complications.
Results: Significantly increased risk of SGA was associated with first and third trimester PM2.5 (particulate matter <2.5 μm in aerodynamic diameter), and increased risk of VSGA associated with first, second and third trimester nitrogen dioxide (NO2) concentrations. Pregnancies complicated by placental abruption and premature rupture of the membrane had ∼two- to fivefold 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.
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Competing interests: None.
Funding: This work was funded by a grant from the Foundation of the University of Medicine and Dentistry of New Jersey (UMDNJ) and the NIEHS-sponsored UMDNJ Center for Environmental Exposures and Disease (CEED), grant no. NIEHS P30ES005022.
Ethics approval: The study was approved by both UMDNJ and NJ Department of Health and Senior Services (NJDHSS) Institutional Review Boards.