Researchers accessed data from the birth registry in Massachusetts for the years 2001–2013 to investigate the possible connection between maternal exposure to residential greenness and birthweight. The study was based on the research-supported understanding that maternal exposure to residential greenness may beneﬁt fetal growth, which in turn decreases the risk of infants being of term low birthweight (TLBW) and small for gestational age (SGA). The Normalized Difference Vegetation Index (NDVI) – an index of plant greenness generated from satellite imagery –for the period of time for each mother's pregnancy was used as a measure of residential greenness.
The birth records of 780,435 out of a total of 978,225 newborns were analyzed. Reasons for excluding some birth records from the study included (a) missing residence information and other relevant personal data (e.g., maternal age, race, education, smoking prior to or during pregnancy, etc.), (b) not live births, (c) not full-term, and (d) birthweight below 500 grams. Overall, the data showed that higher greenness exposure was associated with higher birthweight. This association was stronger for mothers living in less green compared to higher green conditions. Higher greenness exposure was also associated with lower risk of TLBW and SGA. The strongest associations between greenness exposure and decreased risk of TLBW and SGA applied to children born to mothers of higher socioeconomic status, rather than lower socioeconomic status as has been found in prior studies. There was also some evidence of stronger positive associations between greenness and TLBW in high population density areas.
These findings support other research indicating that higher levels of greenness near pregnant women's homes may promote a healthy fetal environment and therefore better fetal growth and healthier birthweights. A finding new to this study relates to the stronger relationship between greenness and birth outcomes for lower levels of greenness. Additional research is necessary, but the authors suggest that increasing low greenness to medium greenness may pay bigger dividends than increasing medium greenness to high greenness. The authors propose that the unexpected findings of stronger associations between healthy birth outcomes and greenness for mothers of higher socioeconomic status, which contrast with prior studies, may be the result of complex patterns related to access to and use of green space depending on socioeconomic status. Again, further research is needed to understand this discrepant finding.