The association between maternal exposure to fine particulate matter (PM_2.5) and gestational diabetes mellitus (GDM): A prospective birth cohort study in China

Although previous studies have proposed an association between maternal exposure to fine particulate matter (PM2.5) and the risk of gestational diabetes mellitus (GDM), such evidence remains rare. Additionally, the effects of PM2.5 on glycemic control in GDM patients are poorly known. In this study, we conducted a prospective birth cohort study in China, and aimed to investigate the association between maternal exposure to PM2.5 and the risk of GDM, identify the susceptible exposure window, and quantify the exposure-response relationships between PM2.5 and fasting glucose in GDM patients. A spatiotemporal land-use-regression model was used to estimate individual weekly PM2.5 exposure during pregnancy. A distributed lag nonlinear model incorporated with a Cox proportional hazard model was used to estimate the association between maternal exposure to PM2.5 and the risk of GDM. Among the 4174 pregnant women in our study, 1018 (24.4%) were diagnosed with GDM. Each 10 μg m-3 increment in PM2.5 exposures during the 24th gestational week was significantly associated with a higher risk of GDM [hazard ratio (HR) = 1.03, 95% CI (confidence interval): 1.01, 1.06]. Compared to the lowest quartile (Q1) of PM2.5 exposure, participants with the highest quartile (Q4) during the 21st-24th gestational weeks had a higher risk of GDM, and the strongest association was observed in the 22nd gestational week (HR = 1.15, 95%Cl: 1.02, 1.28). The mean PM2.5 exposures during the 21st-24th weeks were positively associated with fasting plasma glucose in pregnant women with GDM. Each 10 μg m-3 increase in the mean PM2.5 exposure was associated with a 0.07 mmol l-1 (95% CI: 0.04, 0.11 mmol l-1) increase in the fasting glucose level. Our findings suggest that maternal exposure to higher PM2.5 during pregnancy may increase the risk of GDM, and result in poor glycemic control among pregnant women with GDM. The 21st-24th gestational week period might be the (most)? susceptible exposure window of PM2.5.