Health effects of air pollution on maternal preeclampsia in a rural area of China: A population-based cohort study

Few studies have focused on the effects of air pollutants on maternal preeclampsia and sub-types in rural areas. In this study, a time-dependent Cox proportional hazards model was used to explore trimester-specific and entire pregnancy concentrations of pollutants and preeclampsia in Liuyang rural area of China from 2017 to 2019, and to examine whether season and parity could modify the effects. 36,776 participants were included, of whom 968 (2.63%) were diagnosed with preeclampsia (mild 448; severe 520). Exposure to PM2.5 was significantly asso-ciated with mild preeclampsia (HR 1.12-1.90) in the adjusted models for the overall pregnancy. Exposure to ozone had the opposite effect. SO2 exposure in the third trimester was positively associated with mild pre-eclampsia (HR 1.14-1.35). Exposure to PM10 was associated with a 2% risk of severe preeclampsia in the adjusted models for the first trimester. Mild preeclampsia was positively associated with exposure to NO2 and SO2 in the third trimester in the summer conception, and both sizes of particulate matter in the first trimester in the winter. The risk of preeclampsia was increased by exposure to SO2 in the third trimester for nulliparous women (HR 1.30, 95% CI: 1.12-1.52), PM10 in the first trimester for primiparous women (HR 1.03, 95% CI: 1.01-1.04), and both sizes of particulate matter in the second trimester for multiparous women (HR 1.09, 95% CI: 1.02-1.17; HR 1.07, 95% CI: 1.02-1.13). The study adds to evidence on the association between maternal exposure to air pollutants and different types of preeclampsia.