Increased levels of residential greenness may reduce the risks of negative birth outcomesStudies conducted in multiple countries over the past decade provide evidence of a positive connection between natural vegetation near homes and birth outcomes. The evidence from these studies, however, has been inconsistent, which “makes it difficult to interpret the results and to provide specific suggestions to policy makers.” The aim of this study was to conduct a literature-based health assessment based on epidemiological studies with regard to the association of greenness in the living environment of pregnant women with birth outcomes.
Studies included in this review were identified through a systematic search in three electronic databases: EMBASE, Web of Science, and PubMed. Search terms focused on (1) greenness in the living environment (“greenspace”, “urban green space” “green space”, “natural environment”, “greenness”, “residential greenness”, “vegetation”) and (2) birth outcomes (“birth outcomes”, “adverse birth outcomes”, “birth weight”, “low birth weight”, “preterm birth”, “gestational age”, “small for gestational age”). The search was limited to studies published in English. The last update for the search was July 10, 2020. Twenty-nine studies were included in the review.
Most (15) of the studies were conducted in North America. Others were conducted in Europe (N=7), Asia (N=4), and Oceania (N=1). Two were conducted in multiple countries. The sample size for these studies ranged from 301 to over 3,000,000. Most of the studies used NDVI (Normalized Difference Vegetation Index) as a measure of greenness around maternal addresses at the time of delivery. Birth outcomes were based on medical records and/or register data.
Birth outcomes reported in the studies ranged from one to seven, with most studies reporting “significant decreases in adverse birth outcome risks” with higher levels of residential greenness. The overall analysis showed that for each 0.1 increase in residential greenness, there was a statistically significant increase in birth weight and reduction in the risk of low birth weight. Results also show some evidence of the benefits of mothers living with higher residential greenness on pre-term birth and small for gestational age, but the results are less consistent across the varying buffer sizes of NDVI.
The findings of this review indicate that increased levels of residential greenness may reduce the risks of negative birth outcomes. More research is needed, however, to address some of the concerns identified through this review, including issues relating to how greenness is assessed, the generalizability of the findings, and possible confounding variables impacting the results (air pollution, noise, maternal behaviors, etc.).
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