Prenatal Exposure to Air Pollution and Respiratory Distress in Term Newborns: Results from the MIREC Prospective...

Respiratory distress is the leading cause of neonatal morbidity and mortality worldwide, and prenatal exposure to air pollution is associated with adverse long-term respiratory outcomes; however, the impact of prenatal air pollution exposure on neonatal respiratory distress has not been well studied.

We examined associations between prenatal exposures to fine particular matter (${\mathrm{PM}}_{2.5}$) and nitrogen dioxide (${\mathrm{NO}}_2$) with respiratory distress and related neonatal outcomes.

We used data from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study, a prospective pregnancy cohort ($n=\mathrm{2,001}$) recruited in the first trimester from 10 Canadian cities. Prenatal exposures to ${\mathrm{PM}}_{2.5}$ ($n=\mathrm{1,321}$) and ${\mathrm{NO}}_2$ ($n=\mathrm{1,064}$) were estimated using land-use regression and satellite-derived models coupled with ground-level monitoring and linked to participants based on residential location at birth. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) for associations between air pollution and physician-diagnosed respiratory distress in term neonates in hierarchical logistic regression models adjusting for detailed maternal and infant covariates.

Approximately $7\%$ of newborns experienced respiratory distress. Neonates received clinical interventions including oxygen therapy (6%), assisted ventilation (2%), and systemic antibiotics (3%). Two percent received multiple interventions and 4% were admitted to the neonatal intensive care unit (NICU). Median ${\mathrm{PM}}_{2.5}$ and ${\mathrm{NO}}_2$ concentrations during pregnancy were $8.81{\mu g/m}^3$ and $18.02\text{\hspace{0.17em}ppb}$, respectively. Prenatal exposures to air pollution were not associated with physician-diagnosed respiratory distress, oxygen therapy, or NICU admissions. However, ${\mathrm{PM}}_{2.5}$ exposures were strongly associated with assisted ventilation (OR per ${1\text{-}\mu g/m}^3$ increase in ${\mathrm{PM}}_{2.5}=1.17$; 95% CI: 1.02, 1.35), multiple clinical interventions (OR per $1{\text{-}\mu g/m}^3$ increase in ${\mathrm{PM}}_{2.5}=1.16$; 95% CI: 1.07, 1.26), and systemic antibiotics, (OR per $1{\text{-}\mu g/m}^3$ increase in ${\mathrm{PM}}_{2.5}=1.12$; 95% CI: 1.04, 1.21). These associations were consistent across exposure periods-that is, during prepregnancy, individual trimesters, and total pregnancy-and robust to model specification. ${\mathrm{NO}}_2$ exposure was associated with administration of systemic antibiotics (OR per 1-ppb increase in ${\mathrm{NO}}_2=1.03$; 95% CI: 1.00, 1.06).

Prenatal exposures to ${\mathrm{PM}}_{2.5}$ increased the risk of severe respiratory distress among term newborns. These findings support the development and prioritization of public health and prenatal care strategies to increase awareness and minimize prenatal exposures to air pollution. https://doi.org/10.1289/EHP12880.