Residential greenness and birth outcomes: evidence for reduced low birth weight from an umbrella review and harmonized normalized difference vegetation index synthesis
Abstract
Introduction: Residential green space is increasingly recognized as a potential protective factor for maternal and neonatal health, yet the evidence regarding its association with low birth weight (LBW) and preterm birth (PTB) remains inconsistent. Existing reviews differ substantially in exposure assessment, analytical methods, and reporting standards. The objective of this umbrella review was to evaluate the strength and coherence of current evidence and to generate harmonized quantitative estimates suitable for use in environmental health assessment.
Methods: Systematic reviews published from 2020 to April 2025 were identified using predefined PECOS (Population, Exposure, Comparator, Outcome, Study design) criteria. Review quality was assessed using Measurement Tool to Assess Systematic Reviews (AMSTAR 2) and its environmental health extension (AMSTAR 2-EH). When the body of evidence was judged at least limited, a harmonized meta-analysis of the primary studies included in previous reviews was conducted. Effect estimates were transformed to a common exposure metric corresponding to a 0.1-unit increase in the Normalized Difference Vegetation Index (NDVI) and pooled using random-effects models stratified by residential buffer size.
Results: Nine systematic reviews met the inclusion criteria. The overall evidence was graded as limited for low birth weight and inadequate for preterm birth. The harmonized quantitative synthesis showed consistent reductions in LBW risk in…
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