Influence of residential greenness on adverse pregnancy outcomes: A systematic review and dose-response meta-analysis

Abstract Background With the development of urbanization, there is a decreasing tendency for people contact with natural greenness. Whether maternal exposure to greenness has an impact on pregnancy complications and pregnancy outcomes remains to be confirmed. Objectives To estimate the association and dose-response relationship between residential greenness and pregnancy outcomes. Data sources PubMed, Embase, Ovid, Scopus and Web of Science from inception to 1st December 2019 were searched. Synthesis methods The summary regression coefficient (β) and odds ratio (OR) with corresponding 95% confidence interval (95%CI) were calculated. The linear dose-response relationship between greenness and adverse pregnancy outcomes was also investigated. Results Overall, 36 studies with a total of 11,983,089 participants were included. Birth weight was significantly higher in highest level of greenness exposure group compared to lowest level group (e.g. β:20.22, 95%CI:13.50–26.93 at 100 m buffer). The odds of low birth weight (LBW) decreased in the highest level of group compared to lowest level group (e.g. OR:0.86, 95%CI:0.75–0.99 at 100 m buffer). The odds of small for gestational age (SGA) also decreased in the highest group (OR:0.93, 95%CI:0.88–1.00 at 100 m buffer). In addition, maternal exposure to greenness was associated with increased head circumference and decreased mental disorders. The dose-response models showed a 2% decrease risk of LBW per 0.1 normalized difference vegetation index (NDVI) increase within 300 m buffer (OR:0.98, 95%CI:0.97–0.99, P  Conclusions This review confirms an inverse association between residential greenness and adverse pregnancy outcomes. Findings of our study provide evidences for pregnant women to increase greenness exposure.