Associations between neighborhood greenspace and multiple birth outcomes across two metropolitan areas in Australia

Background: Beneficial effects of greenspace on birth outcomes have been reported. However, insights on key windows of exposure and underlying mechanisms are needed.Method: Births in Sydney (2016-2019) were retrieved from NSW Midwives Data Collection. Births in Brisbane (2000-2014) were retrieved from Queensland Health Perinatal Data Collection. Satellite image-derived normalized difference vegetation index (NDVI) and night time light (NTL) index were used. For each city, linear regression models were used to assess associations between greenspace and birth weight, and logistic models to estimate the risks of pre -term birth (PTB), low birth weight (LBW), and small for gestational age (SGA) per 0.1 increase in NDVI. We examined the trimester-specific associations, and heterogeneities by night time light.Results: The study included 193,264 singleton births in Sydney and 155,606 singleton births in Brisbane. An 0.1 in-crease in greenspace during whole pregnancy was associated with 17.4 g (95%CI: 14.5 to 20.2) increase in birth weight in Sydney, and 15.1 g (95%CI: 12.0 to 18.5) in Brisbane. The odds ratios were 0.98 (95%CI: 0.97 to 0.99) for LBW, 0.99 (95%CI: 0.98 to 1.00) for PTB, and 0.98 (95%CI: 0.96 to 0.99) for SGA per 0.1 increase in NDVI during whole pregnancy for participants in Sydney. Similarly, reduced odds of adverse birth outcomes were observed in Brisbane. Trimester specific models demonstrated a consistent pattern of associations in the same direction across all outcomes. We found that effects of greenspace exposure on birth outcomes attenuated after adjusting for NTL, but stronger effects among babies of mothers from areas with more NTL.Conclusions and relevance: These findings suggest a beneficial association between neighborhood greenspace and healthier pregnancies in urban areas. We provide novel evidence of interactions between greenspace and NTL.