Does the spatial scale of greenness matter? Evidence from pregnant women in urban Ontario, Canada

Background

Neighbourhood greenness is associated with metabolic health, yet the spatial scale at which these associations operate remains unclear, particularly among pregnant women.

Methods

We conducted a population-based cohort study of pregnancies among women aged 19–45 years from urban communities in Ontario, Canada, using linked administrative health data. Greenness was measured using the Normalized Difference Vegetation Index (NDVI) within 250 m, 500 m, and 1000 m buffers around maternal residential dissemination areas at the time of their index pregnancy. Gestational diabetes mellitus (GDM) was identified using a validated algorithm based on hospital and outpatient records. Associations were estimated using generalized estimating equation logistic regression models accounting for clustering by mother and adjusting for maternal age, parity, immigration status, and neighbourhood income.

Results

The analytic sample included 1,924,926 pregnancies, with higher greenness levels concentrated in higher-income neighbourhoods. Higher greenness was associated with lower odds of GDM across all buffer sizes, with a clear gradient by spatial scale. Adjusted odds ratios were 0.70 (95% CI: 0.65–0.74) at 250 m, 0.78 (0.73–0.84) at 500 m, and 0.82 (0.77–0.88) at 1000 m. Associations were strongest at smaller buffers, indicating that immediate residential greenness may be most relevant for GDM risk.

Conclusions

Greenness closer to home is more strongly associated with reduced GDM risk. Proximity appears to be a key dimension of greenness exposure, as nearby environments may better support daily mobility, walkability, stress reduction, and mental well-being during pregnancy, while larger buffers may include less accessible spaces. Urban planning strategies should prioritize accessible, small-scale green infrastructure within residential neighbourhoods to enhance maternal health and well-being.

Key messages

• Greenness closer to home shows stronger associations with lower GDM risk, highlighting the importance of immediate neighbourhood environments.

• Urban planning should prioritize accessible, small-scale green spaces to support walkability, mental well-being, and maternal health during pregnancy.