Exploring pathways between residential greenness and antepartum stillbirth: A mediation analysis

Background: Antepartum stillbirth is an important public health issue. This study aimed to identify mediation pathways from the vegetation greenness surrounding the maternal residence to antepartum stillbirth, through stillbirth risk factors. Methods: This study is part of the FetRisks project–a population-based case–control study of stillbirth and live births in 14 public hospitals in the Municipality of São Paulo, Brazil (December 2019–December 2023). We estimated vegetation greenness using the median value of the normalized difference vegetation index (NDVI) obtained from satellite images from the study period, considering buffer radii around the residences between 50 and 500 m. We used penalized logistic regressions to select maternal, placental, fetal, and neighborhood characteristics. Based on these data, we built a Bayesian network and performed counterfactual mediation analyses. Results: We analyzed 248 antepartum stillbirths (cases) and 301 live births (controls). The maternal residence of 19.4% (48/248) of cases and 30.9% (93/301) of controls had a median NDVI within a buffer radius of 150 m (NDVI-150m) greater than 0.104. Women living in residences with a median NDVI-150m greater than 0.104 had a lower risk of antepartum stillbirth (odds ratio: 0.50; 95% confidence interval [CI]: 0.33, 0.76). Fetal growth restriction and placental inflammatory signs mediated 38.5% (natural indirect effect: −0.0604; 95% CI: −0.0916, −0.0292) and 14.7% (natural indirect effect: −0.0230; 95% CI: −0.0412, −0.0047) of the effect of a median NDVI-150m greater than 0.104 on antepartum stillbirth, respectively. Conclusion: Higher residential vegetation greenness showed protective indirect effects on antepartum stillbirth partially through a lower risk of fetal growth restriction and placental inflammatory signs.