Air pollution exposure during pregnancy and low birth weight and macrosomia: the role of gestational diabetes mellitus.

BACKGROUND: The relationship between environmental air pollution and birth weight has been established, However, there is limited research exploring the role of gestational diabetes in the relationship between air pollution exposure and birth weight. This study aimed to investigate whether gestational diabetes influences the association between air pollution exposure and birth weight. METHODS: A retrospective cohort study of 33,060 primiparous pregnancies between 2017 and 2022. Satellite-based estimates were employed for the five air pollutants (PM2.5, PM10, NO2, CO, and O3). Multilevel logistic regression analyses were conducted, adjusting for individual and conception season. The moderating effect analyses was used to assess the role of gestational diabetes mellitus (GDM) in the association of pollutant exposure with low birth weight (LBW) and macrosomia at different trimesters of pregnancy. Additionally, sensitivity analyses were performed. RESULTS: The results showed that exposure to air pollution during pregnancy increased the risk of both LBW and macrosomia. Additionally, exposure to air pollution during specific pregnancy periods significantly increased the risk of macrosomia in GDM patients. The study also observed the moderating effect of GDM on the relationship between air pollution exposure and pregnancy outcomes. In T1, GDM moderated the relationship between exposure to PM2.5 (β = -0.018, P = 0.029) and NO2 (β = -0.024, P = 0.048) and the risk of LBW. Furthermore, GDM also moderated the relationship between exposure to PM2.5 (β = 0.015, P = 0.013), PM10 (β = 0.018, P < 0.001), NO2 (β = 0.027, P = 0.002), CO (β = 0.001, P = 0.011) in T1, exposure to O3 (β = 0.013, P = 0.015) in T2, and exposure to NO2 (β = 0.024, P = 0.016) in T3, and the risk of macrosomia. CONCLUSION: Gestational diabetes significantly moderated the relationship between air pollution and birth weight. This study underscored the hazards of air pollution on maternal and newborn populations, and underlined targeted protection in susceptible subgroups.