# Antepartum Exposure to Greenness, Air Pollution, and Temperature and Outcomes of Preterm Infants

## TL;DR

This study finds that prenatal exposure to high ozone, low greenness, and low temperatures is linked to worse outcomes for extremely preterm infants.

## Contribution

The study identifies specific environmental factors associated with neonatal outcomes in preterm infants using a large Canadian cohort.

## Key findings

- High ozone exposure during pregnancy is linked to lower odds of survival without major morbidity in preterm infants.
- Low greenness and low temperature combined with high ozone further reduce survival odds in preterm infants.
- Environmental stressors during pregnancy affect neonatal outcomes in infants born before 29 weeks.

## Abstract

This cohort study investigates the association between prenatal exposure to environmental factors and outcomes among infants born between 22 and 28 weeks’ gestation in Canada.

Is antepartum exposure to green spaces, air pollutants, and extreme temperatures associated with the neonatal outcomes of preterm infants?

In this cohort study of 14 748 extremely preterm infants that used data from linked national environmental and neonatal databases, maternal antepartum exposure to low levels of greenness, high levels of ozone, and low temperatures was associated with significantly lower odds of survival without major morbidity in infants compared with infants born to mothers who were unexposed.

The findings suggest that antepartum exposure to environmental stressors is associated with neonatal outcomes of infants born before 29 weeks’ gestation.

Existing evidence shows that the environment is a risk factor in preterm birth. However, more evidence is needed about the association between environmental exposures and outcomes of preterm birth.

To examine the association of antepartum exposure to individual and combined indices of greenness, air pollution, and extreme temperatures with outcomes of preterm infants.

This cohort study used linked national databases of the Canadian Neonatal Network and Canadian Urban Environmental Health Research Consortium. The cohort consisted of infants born at 22 to 28 weeks plus 6 days’ gestation between January 1, 2010, and December 31, 2020, and treated in tertiary neonatal intensive care units (NICUs) across Canada. Data were analyzed between May 1 and September 15, 2024.

Indices summarizing levels of greenness, air pollutants, and ambient temperature at mothers’ residential postal code at birth.

Infant survival without major morbidity (SWMM) assessed at death or discharge from the NICU. Logistic regression models estimated associations between individual and combination of indices with SWMM.

A total of 14 748 infants (7965 males [54.0%]; mean [SD] gestational age, 26.1 [1.6] weeks; median [IQR] birth weight, 890 [720-1090] g) were included. The rate of SWMM was 32.1% (4737 of 14 748). Infants born to mothers who were exposed to high ozone levels had lower odds of SWMM vs infants with mothers exposed to low ozone levels (adjusted odds ratio [AOR], 0.83; 95% CI, 0.74-0.95). Infants with antepartum exposure to low temperature combined with either high levels of ozone (AOR, 0.76; 95% CI, 0.60-0.95) or low levels of greenness (AOR, 0.77; 95% CI, 0.60-0.99) or both low levels of greenness and high levels of ozone (AOR, 0.58; 95% CI, 0.43-0.77) had lower odds of SWMM than infants with mothers who were not exposed to these risk factors.

In this cohort study, antepartum exposure to high ozone and combined low temperatures and low levels of greenness or high ozone were associated with lower odds of SWMM in preterm infants. These findings suggest that the health outcomes of antepartum environmental exposure extend to neonatal outcomes of preterm infants.