Gestational diabetes mellitus (GDM) confers substantial short- and long-term metabolic complications for mothers and offspring; however, whether GDM should be screened for and managed in early pregnancy remains debated, and the standardized definition and optimal screening window for Chinese women remain controversial. We conducted a series of analyses of the Tianjin cohort, China, to evaluate the clinical significance of fasting plasma glucose (FPG) in early pregnancy for adverse pregnancy outcomes and postpartum diabetes risk.

The first cohort study (n=19,134) identified a distinct threshold of FPG 5.1–6.9 mmol/L at 9–19 gestational weeks as a valid definition for early GDM, with this glycemic range associated with a significantly increased risk of composite adverse pregnancy outcomes (CAPO) (adjusted OR=1.18, 95%CI: 1.09–1.29), macrosomia (adjusted OR=1.28, 95%CI: 1.15–1.44) and large for gestational age (LGA) (adjusted OR=1.27, 95%CI: 1.15–1.41); in contrast, elevated FPG before 9 gestational weeks showed no such risk association, indicating a critical gestational age–dependent effect. The second cohort study (n=504) demonstrated that early-pregnancy FPG further stratified postpartum diabetes risk among Chinese women with GDM: FPG 5.6–6.9 mmol/L before 20 gestational weeks was associated with a markedly increased risk of postpartum diabetes (adjusted OR=7.87, 95%CI: 2.65–23.4), whereas FPG 5.1–5.5 mmol/L showed no significant association.

Collectively, these findings support 9–19 gestational weeks as the optimal screening window for early screening and FPG 5.1–6.9 mmol/L (with a 5.6 mmol/L threshold for prediction of postpartum diabetes) as the pragmatic diagnostic criterion for early GDM in Chinese women, providing an evidence-based rationale for early risk stratification, targeted intervention, and improved long-term maternal metabolic health management.

Ming Gao, PhD, is a lecturer in the Department of Epidemiology and Biostatistics, School of Public Health, Tianjin Medical University. Her research focuses on the epidemiology and molecular epidemiology of gestational diabetes mellitus and type 2 diabetes mellitus. She has authored more than 10 publications as first author in leading diabetes and endocrinology journals, including Obesity Reviews and Diabetes Care.