Associations of Pre‐Pregnancy and Prenatal Outdoor Nighttime Light, Green Space and Neighbourhood Walkability With Preterm Birth: Results From Ruian Birth Cohort Study

Background Epidemiological studies have reported associations between the built environment and adverse pregnancy outcomes, but research examining sensitive time windows and the potential interaction effects between exposures remains limited. Objectives To examine how built environment relates to preterm birth (PTB) and potential interaction effects between exposures. Methods Based on 2418 pregnant women from the Ruian Birth Cohort Study (RBCS), we assessed pre‐pregnancy and prenatal artificial light at night (ALAN), normalised difference vegetation index (NDVI) and neighbourhood walkability in relation to PTB risk via Cox regression models, and examined interactions and sensitive periods. Results Pre‐pregnancy and prenatal NDVI were associated with decreased preterm risk [Hazard ratio (HR) pre‐ pregnancy 0.83, 95% confidence interval (CI) 0.70, 0.99; HR 7–9 months before pregnancy 0.84, 95% CI 0.71, 1.00; HR 4‐6 months before pregnancy 0.84, 95% CI 0.71, 1.00; HR prenatal 0.79, 95% CI 0.66, 0.93; HR First trimester 0.78, 95% CI 0.66, 0.93; HR Second trimester 0.82, 95% CI 0.70, 0.97; HR Third trimester 0.79, 95% CI 0.67, 0.93]. Pre‐pregnancy ALAN showed a nonlinear association with PTB. ALAN interacted with both neighbourhood walkability [relative excess risk due to interaction (RERI) −5.99, 95% CI −10.15, −1.83; attributable proportion due to interaction (AP) −1.58, 95% CI −2.74, −0.41] and NDVI (RERI pre‐ pregnancy −2.16, 95% CI −3.99, −0.32; AP pre‐ pregnancy −0.82, 95% CI −1.67, 0.03; RERI prenatal −2.86, 95% CI −4.99, −0.73; AP prenatal −1.31, 95% CI −2.38, −0.24). Conclusions ALAN showed a non‐linear association with PTB risk: low to moderate levels were linked to increased risk, whilst high ALAN levels did not increase risk. Green space was linked to lower PTB risk. Negative additive interactions were found between ALAN and green space, as well as between ALAN and neighbourhood walkability, indicating that the associations of green space and neighbourhood walkability and PTB were stronger when ALAN was at higher levels.