Maternal green space exposure and congenital heart defects: A population-based study

Beneficial effects of maternal green space exposure on preterm birth and low birth weight have been documented, but few studies have investigated its protective effect on fetal congenital heart defects (CHDs). Our study aimed to investigate the association between maternal green space exposure and CHDs, and quantify the potential benefits of reducing the risk of fetal CHDs by achieving the target of green space coverage.

The study included 4160 births with CHDs and 567,483 births without birth defects born from 2014 to 2019 in 14 cities in Liaoning Province, China. Maternal green space exposure, including periconception period (3 months before conception to 3 months into pregnancy), preconception period (3 months before conception), and the first trimester (3 months into pregnancy), was assessed using satellite-based normalized difference vegetation index (NDVI). Logistic regression models were used to estimate the associations between maternal green space exposure and the risk of fetal CHDs.

A 0.1-unit increase in maternal green space exposure during the periconception was significantly associated with 5% declines in the risk of CHDs (OR: 0.95, 95% CI: 0.92, 0.98). Exposure-response association suggested that continuous improvements in maternal green space exposure during the periconception had a greater protective impact on the risk of total CHDs, while attenuated benefits were identified in the area where NDVI is around 0.23. Assuming causality, 5.06% (95% CI: 1.72%, 8.28%) of the annual rate of CHDs could be avoided by increasing NDVI exposure to 0.23 during periconception period in the areas where NDVI is below 0.23. In addition, rural residents, and mothers who have parity twice or more, were more prone to the protective effect of green space exposure.

Our study provides evidence that maternal green space exposure is a protective factor against the risk of fetal CHDs. The findings suggest that prioritizing green space in public policy can be an effective health-promoting measure.