Ambient air pollution and the risk of stillbirth: a population-based prospective birth cohort study in the coastal area of China

Accumulating evidence has shown that prenatal ambient air pollution exposure is associated with elevated stillbirth risk; however, the results are inconsistent. This population-based prospective cohort study aimed to explore the association between prenatal air pollution exposure and stillbirth rate in the coastal area in China. Data of air pollution and birth outcomes between January 1, 2015, and December 31, 2017, were collected. Among the 59,868 eligible births, there were 587 stillbirths and 59,281 live births. Although the air quality in this study was relatively better than most of the major cities in China, a positive association was still found between prenatal air pollution exposure and stillbirth rate. Every 10 μg/m3 increase of fine particulate matters (PM2.5) in each trimester, as well as in the entire pregnancy, was associated with increased stillbirth rate (RR = 1.14, 1.11, 1.15, and 1.14 for the first, second, third trimester, and entire pregnancy, respectively). In addition, every 10 μg/m3 increase of PM10 in the first trimester (RR = 1.09, 95% CI: 1.04–1.14), and 10 μg/m3 increase of O3 in the first (RR = 1.05, 95% CI: 1.01–1.09) and third (RR = 1.04, 95% CI: 1.00–1.08) trimesters was also associated with increased stillbirth rate. The effects of PM2.5 on stillbirth rate were found to be robust in the two-pollutant models. The findings of this study especially underscored the adverse effects of prenatal exposure of high levels of PM2.5 on stillbirth. More studies are needed to verify our findings and further investigate the underlying mechanisms.