Associations between neighborhood greenery and birth outcomes in a North Carolina cohort

Higher levels of neighborhood greenery have been associated with improved birth outcomes. However, many studies use metrics relying on vegetation density and are not able to distinguish types of greenery or spatial context, which may result in variation in potential benefits.

We examined relationships between term low birth weight (TLBW) and preterm birth (PTB), and different types of neighborhood greenery (i.e., tree cover, herbaceous cover, and aggregate greenery) within various spatial contexts (i.e., Euclidean distance and network distance-based buffers, and busy roadways to represent overall, street, and near-road greenery).

North Carolina birth registry data from 2003 to 2015 were used to create a singleton live birth cohort and linked to greenery metrics from EnviroAtlas. Logistic regression models were used to estimate OR (95%CI) for associations between greenery metrics and TLBW (<2500 g) or PTB (<37 weeks gestational age) adjusting for potential confounders. Analyses were stratified by race/ethnicity, as many studies report potential differences in proximity to greenery across these groups.

We observed modest associations between multiple measures of neighborhood greenery and TLBW and PTB. Most of our results indicated a decreased odds of adverse birth outcomes with increasing levels of neighborhood greenery, but some associations showed increased odds of adverse birth outcomes. We observed the strongest associations between overall aggregate greenery with TLBW (0.967 [0.939, 0.996]) and near-road tree cover with PTB (0.985 [0.971, 0.999]). We also observed unexpected associations between increased greenway density and TLBW among non-Hispanic Black mothers (1.181 [1.049, 1.326]). In contrast, we observed a decreased odds of PTB associated with increased greenway density for non-Hispanic white mothers (0.926 [0.871, 0.983]).

We examined relationships between adverse birth outcomes and different types of neighborhood greenery, generally finding decreased odds of adverse birth outcomes with increasing levels of neighborhood greenery, with the strongest associations between aggregate greenery based on the Euclidean distance and decreased odds of term low birth weight. However, we also observed unexpected associations with increased greenway density and increased term low birth weight among non-Hispanic Black mothers. These results highlight the importance of considering the ways greenspace may or may not benefit some communities and will be important in guiding future efforts to increase instorative value or restore neighborhood greenspaces.