Residential greenspace counteracts PM_2.5 on the risks of preterm birth subtypes: A multicenter study

The association between residential greenspace and preterm birth (PTB) risk remained inconclusive. The PTB subtypes have been ignored and the effect of co-exposure of PM_2.5 on PTB risk is still unclear.

To investigate the independent, interactive, and mixed effects of residential greenspace and PM_2.5 on the risk of PTB subtypes.

A total of 19,900 singleton births from 20 hospitals in Shanghai, China, from 2015 to 2017 were included. The Normalized Difference Vegetation Index (NDVI) within 500 m and 1000 m buffers of the maternal residence and a combined geoscience-statistical model-derived PM_2.5 and its six components were used as the exposure measures. PTB (<37 completed weeks of gestation) were divided into early PTB (24-33 weeks) vs. late PTB (34-36 weeks) and into spontaneous PTB (sPTB), preterm premature rupture of the fetal membranes (PPROM), and iatrogenic PTB. Multivariable logistic regression models were applied to assess the independent and interactive effects of NDVI and PM_2.5 on PTB in each trimester. The quantile g-computation approach was employed to explore the mixture effect of PM_2.5 components and greenspace across the pregnancy and to determine the main contributors.

Levels of PM_2.5 and greenspace were associated with increased [aOR (95%CI) ranging from 1.18 (1.07, 1.30) to 3.36 (2.45, 4.64)] and decreased risks [aORs (95%CI) ranging from 0.64 (0.53, 0.78) to 0.86 (0.73, 0.99)] of PTB subtypes, respectively. At the same PM_2.5 level, higher residential greenspace was associated with lower risks, and vice versa. All these associations were more pronounced in late pregnancy. Early PTB and PPROM were the main affected subtypes, and the main drivers in PM_2.5 were black carbon and ammonium.

Residential greenspace may mitigate the PTB risks due to PM_2.5 exposure during pregnancy.