Growing research investigates the perinatal health benefits of greenspace in a mother's prenatal environment. However, evidence of associations between residential greenspace and birth outcomes remains mixed, limiting the relevance this work holds for urban policy and greening interventions. Past research relies predominantly on cross-sectional designs that are vulnerable to residential selection bias, and rarely tests effect modification by maternal race/ethnicity, which may contribute to heterogeneous findings. This study uses a rigorous, longitudinal sibling comparison design and maternal fixed effect analyses to test whether increases in maternal exposure to residential greenspace between pregnancies precede improved birth outcomes among non-Hispanic (NH) white (n = 247,285) and Black (n = 54,995) mothers (mean age = 28 years) who had at least two consecutive live births in California between 2005 and 2015. Results show that increases in residential greenspace correspond with higher birthweight (coef. = 75.49, 95% CI: 23.48, 127.50) among Black, but not white (coef. = -0.51, 95% CI: -22.90, 21.90), infants. Additional analyses suggest that prior evidence of perinatal benefits associated with residential greenspace among white mothers may arise from residential selection; no such bias is observed for Black mothers. Taken together, these findings support urban greening initiatives in historically under-resourced neighborhoods. Efforts to evenly distribute residential greenspace may reduce persistent racial disparities in birth outcomes, an important step towards promoting health equity across the life course.
Keywords: birth outcomes; greenspace; health disparities; natural environment; nature; perinatal health; pregnancy.