Residential proximity to greenness and adverse birth outcomes in urban areas: Findings from a national Canadian population-based study

2022  Journal Article

Residential proximity to greenness and adverse birth outcomes in urban areas: Findings from a national Canadian population-based study

Pub TLDR

The study investigates the relationship between residential proximity to greenness and adverse birth outcomes in urban Canada, finding that mothers living in greener areas have a lower risk of low term birth weight, preterm birth, and small for gestational age babies. These associations remain significant even after accounting for air pollution and are consistent across different socioeconomic statuses, suggesting that greenness positively impacts pregnancy health for all mothers.

 

College of Health researcher(s)

OSU Profile

Highlights

  • Residential greenness was associated with reduced risks of preterm birth, term low birth weight and small for gestational age.
  • Ambient NO2 and PM2.5 increased the risk of adverse birth outcomes independently from greenness.
  • Urban greenness reduced the risk of adverse pregnancy outcomes regardless of neighbourhood socioeconomic status.

Abstract

Background

Over the last decade, several studies have reported that residential proximity to vegetation, or ‘greenness’, is associated with improved birth outcomes, including for term birth weight (TBW), preterm birth (PTB), and small for gestational age (SGA). However, there remain several uncertainties about these possible benefits including the role of air pollution, and the extent to they are influenced socioeconomic status.

Methods

We addressed these gaps using a national population-based study of 2.2 million singleton live births in Canadian metropolitan areas between 1999 and 2008. Exposures to greenness, fine particulate matter (PM2.5), and nitrogen dioxide (NO2) were assigned to infants using the postal code of their mother's residence at the time of birth. The Normalized Difference Vegetation Index (NDVI) was used to characterize greenness, while estimates of ambient PM2.5 and NO2 were estimated using remote sensing, and a national land-use regression surface, respectively. Multivariable regression analysis was performed to describe associations between residential greenness and the birth outcomes. Stratified analyses explored whether these associations were modified by neighbourhood measures of socioeconomic status.

Results

Mothers who lived in greener areas had a lower risk of low TBW, PTB, and SGA babies. These associations persisted after adjustment for ambient NO2 and PM2.5. Specifically, in fully adjusted models, an interquartile range (IQR = 0.16) increase in the NDVI within a residential buffer of 250 m yielded odds ratios of 0.93 (95% confidence interval (CI): 0.92, 0.94), 0.94 (95% CI: 0.92, 0.95), and 0.94 (95% CI: 0.93, 0.95) for the outcomes of PTB, low TBW, and SGA, respectively. Similarly, an IQR increase in greenness was associated with a 16.3 g (95% CI: 15.3, 17.4) increase in TBW. We found inverse associations between greenness and the occurrence of adverse birth outcomes regardless of the socioeconomic status of the neighbourhood.

Interpretation

Our findings support the hypothesis that residential greenness contributes to healthier pregnancies, that these associations are independent from exposure to air pollution. , and that proximity to greenness benefits all mothers regardless of socioeconomic status.

Villeneuve, P.J., Lam, S., Tjepkema, M., Pinault, L.L., Crouse, D.L., Osornio-Vargas, A.R., Hystad, P., Jerrett, M., Lavigne, É., Stieb, D.M.(2022)Residential proximity to greenness and adverse birth outcomes in urban areas: Findings from a national Canadian population-based studyEnvironmental Research204
 
Publication FAQ

FAQ: Potential Benefits of Residential Greenness on Adverse Birth Outcomes

What was the primary aim of the study?

This Canadian population-based study investigated the potential benefits of residential greenness on adverse birth outcomes. The study analyzed data from over 2.2 million singleton live births in Canadian metropolitan areas between 1999 and 2008. The objective was to determine whether residing in greener areas is associated with a lower risk of preterm birth, low term birth weight, and small for gestational age, even after accounting for air pollution and socioeconomic factors.

How was greenness measured in the study?

Greenness was measured using the Normalized Difference Vegetation Index (NDVI), derived from satellite imagery. NDVI measures the intensity of green biomass based on the reflectance of visible (red) and near-infrared light from the Earth's surface. Higher NDVI values indicate a greater presence of green vegetation. Researchers calculated the average NDVI within a 250-meter radius around the mother's residence at the time of birth.

What were the key findings of the study?

The study found that mothers living in greener areas experienced a lower risk of adverse birth outcomes. Specifically, a higher NDVI (indicating more greenness) was associated with a reduced risk of preterm birth, low term birth weight, and small for gestational age. Additionally, an increase in greenness was linked to a higher term birth weight.

Did the study consider the influence of air pollution?

Yes, the study accounted for potential confounding by air pollution. The researchers included measures of fine particulate matter (PM2.5) and nitrogen dioxide (NO2) in their analyses. Notably, the beneficial associations between greenness and birth outcomes remained significant even after adjusting for these air pollutants.

Did socioeconomic status modify the observed associations?

The researchers explored whether the relationship between greenness and birth outcomes varied depending on the socioeconomic status of the neighborhood. They found that the inverse associations between greenness and adverse birth outcomes persisted across all socioeconomic levels. This suggests that the benefits of greenness extend to mothers regardless of their socioeconomic background.

Were there regional variations in the findings?

The study investigated regional differences in the associations between greenness and birth outcomes by stratifying the data by province. While inverse associations were generally observed across all regions, the strength of these associations varied. Notably, more pronounced associations were found in highly urbanized regions, possibly due to better spatial resolution of postal codes and exposure assessment.

Did the study consider seasonal variations?

The study examined associations between greenness and birth outcomes across different months of birth. The findings indicated minimal variation in the observed odds ratios for preterm birth across the 12 months. Similarly, the positive association between greenness and birth weight was consistent throughout the year.

What are the implications of the study's findings?

The study provides strong evidence for the beneficial effects of residential greenness on pregnancy outcomes. These findings reinforce the importance of green spaces in urban planning and design to promote maternal and child health. The study highlights that access to green spaces can benefit all mothers, irrespective of their socioeconomic status, and could potentially contribute to reducing health disparities.