Impact of ambient air pollution exposure during preconception and pregnancy on risk of gestational diabetes mellitus: A retrospective cohort study in China

The association between air pollution exposure and gestational diabetes mellitus (GDM) have been studied extensively; however, conclusions regarding the sensitive exposure period and effect of exposure remain inconsistent. We conducted a retrospective cohort study involving 2593 pregnant participants from Kunshan, China. Daily concentrations of particulate matter less than 2.5 μm (PM_2.5) and less than 10 μm (PM₁₀), carbon monoxide (CO), nitrogen dioxide (NO₂), and sulfur dioxide (SO₂) data were collected from the nearest air quality monitoring stations based on each participant's address. Average pollutant concentrations were then calculated for various window periods. The prevalence rate of GDM was 11.7 %. The first trimester was identified as a critical exposure window using distributed lag non-linear models. Quantile-based g-computation analysis revealed that exposure to a mixture of the five pollutants during the first trimester was significantly associated with GDM risk. Specifically, each quartile increase in combined exposure was associated with a 45 % increased risk of GDM (RR=1.45, 95 % CI: 1.24, 1.70), primarily driven by SO₂ (31.6 %), PM_2.5 (31.6 %), CO (22.0 %), and PM₁₀ (14.8 %). This effect was not observed for exposure to any single pollutant alone. Our study expands the methodology for assessing air pollution exposure and deepens scientific understanding of its impact on pregnancy outcomes.