Ambient air pollution as a modifiable risk factor for gestational diabetes mellitus: A narrative review

Gestational diabetes mellitus (GDM) represents a growing global health challenge, affecting 14%–25% of pregnancies and substantially increasing the lifetime risk of type 2 diabetes for both mother and offspring. This structured narrative review synthesizes epidemiological and experimental evidence implicating ambient air pollution—particularly fine particulate matter (PM2.5), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and carbon monoxide (CO)—as a significant, modifiable contributor to GDM development. Multiple meta-analyses encompassing millions of pregnancies confirm significant associations between common air pollutants and elevated GDM risk, though the magnitude and consistency of these associations vary by pollutant, gestational timing, and study setting. Proposed biological mechanisms include oxidative stress impairing pancreatic beta-cell function, pollutant-driven systemic inflammation promoting insulin resistance, endocrine disruption altering thyroid and cortisol regulation, mitochondrial dysfunction, and gut microbiome dysbiosis. Preconceptional, first-trimester, and second-trimester windows represent periods of heightened vulnerability, each corresponding to distinct physiological processes. These temporal windows are biologically plausible but remain incompletely characterised. Maternal obesity, household air pollution, and socioeconomic disadvantage meaningfully modify these associations. Targeted clinical counseling, stricter regulatory standards, and prospective multipollutant research are urgently needed to reduce the reproductive health burden of air pollution exposure.