Residential green and blue space effects on newborn health: findings from a retrospective longitudinal study in Wales

The effects of green and blue spaces on newborn health are unclear with most studies using cross-sectional methods. Our retrospective longitudinal study aimed to investigate the effects of green and blue spaces on incidence of low birthweight and pre-term birth, and changes in birthweight (g) and gestational age (weeks). Our cohort was limited to births in Wales (2008 - 2019). Exposures were greenness at a 300m buffer (Enhanced Vegetation Index) and distances to blue spaces (1600m buffer), centred around a mother's home. Annual metrics were derived for the year pre-pregnancy and during-pregnancy. We utilised generalised linear models and controlled for individual-level confounders (e.g. mother's educational attainment) using census data. We conducted moderation analyses using mother's employment status and area-level deprivation. Our cohort comprised 176 459 births. Ten percent greater greenness pre-pregnancy was associated with an increase of 3.04g (95% CI 0.33 - 5.76g, p = 0.03) in birthweight. Further, 10% greater greenness pre-pregnancy was associated with a 1.0-week (p = 0.01) increase in gestational age. There were no greenness effects on pre-term birth or low birthweight. Increasing during-pregnancy distance between home and blue space was associated with increased gestational age (β = 1.0-week, p = 0.01). Greater greenness and living in moderately deprived areas were associated with increased birthweights. Our results indicate that greenness is associated with increases in birthweight and gestational age, while larger distances to blue space are associated with gestational age. The effect of green spaces on birth outcomes is not homogeneous based on area-level deprivation.