High temperature, PM_2.5, greenspace and hypertensive disorders of pregnancy: Exploring interactive effects during...

Hypertensive disorders of pregnancy (HDP) are a leading cause of maternal death. While ambient temperature and air pollution have each been linked to HDP, evidence regarding their combined effects and the modifying roles of relative humidity and green space remains limited.

To examine whether ambient temperature modifies the association between fine particulate matter (PM₂.₅) exposure and HDP risk, and to assess the interactive effects of PM₂.₅, relative humidity, and green space in Chongqing, China.

We conducted a cross-sectional study including 48,160 pregnant women who delivered in a hospital in Chongqing between January 2021 and December 2023. Environmental data on temperature, PM₂.₅, relative humidity, and green space were obtained from local monitoring stations. Generalized linear mixed models were applied to estimate associations between environmental exposures and HDP, adjusting for potential covariates and incorporating interaction terms among PM₂.₅, relative humidity, and green space.

Elevated temperature exposure potentiated the association between PM₂.₅ and HDP, with an adjusted odds ratio (aOR) of 1.11 (95%CI: 1.02-1.20). After including interaction terms, the effect remained pronounced under high-temperature conditions, with aORs of 1.10 (95%CI: 1.07-1.15) in the heat-exposure group and 1.08 (95%CI: 1.02-1.13) in the cold-exposure group. The first trimester was identified as a critical exposure window for PM₂.₅-related HDP risk.

In Chongqing, high temperature exacerbates the association between PM₂.₅ exposure and the incidence of HDP. The interactions among green space, relative humidity, and PM₂.₅ further modify this relationship, highlighting the complex interplay of environmental factors in the etiology of HDP.