BACKGROUND: Gestational diabetes mellitus (GDM) is a growing public health concern, particularly in regions with diverse ethnic populations. Understanding the incidence and risk factors of GDM is crucial for early prevention and management, especially in underrepresented areas like Guizhou Province, China, where geographic and ethnic diversity may influence the disease's prevalence and risk profiles. AIM: To investigate the incidence of GDM and identify its associated risk and protective factors among different ethnic groups in Guizhou Province, providing essential data for early prevention strategies. METHODS: A multi-center retrospective study was conducted, dividing participants into GDM and non-GDM groups according to standardized diagnostic criteria. Data were collected from 103629 deliveries across 40 hospitals in Guizhou. Various demographic, clinical, and laboratory parameters were analyzed using logistic regression to identify risk and protective factors for GDM. RESULTS: Among the 103629 deliveries, 18957 cases of GDM were identified, with an incidence of approximately 18.3%. The risk of GDM was higher in the Han ethnic group compared to minority ethnic groups. The Dong ethnic group had the lowest incidence among the minorities. Key risk factors identified included older age (especially >
35 years), higher pre-pregnancy body mass index (BMI), light physical activity, gravidity, family history of diabetes, hemoglobin, aspartate aminotransferase, alanine aminotransferase, and direct bilirubin. Protective factors included higher education level, total protein, and albumin. There were also differences based on blood type, with type A associated with higher risk. CONCLUSION: The incidence rate in Guizhou is 18.3%. Older age (especially >
35 years), Han ethnicity, lower education level, higher pre-pregnancy BMI, light physical activity, and higher gravidity are the main risk factors for GDM. Laboratory findings indicate that higher hemoglobin, higher liver function parameters (alanine aminotransferase, aspartate aminotransferase, and direct bilirubin), and lower total protein and albumin are associated with a higher risk of GDM. Blood type A has a higher risk of GDM compared to blood types AB and O.