Background
Gestational diabetes mellitus (GDM), affecting approximately 14.7% of pregnancies in the Western Pacific region, is characterized by glucose intolerance first recognized during pregnancy and carries significant risks of adverse maternal and neonatal outcomes, including macrosomia, cesarean delivery, and preeclampsia. Although diagnostic criteria mainly rely on oral glucose tolerance test (OGTT) glucose thresholds, this glucose-centric approach overlooks the considerable metabolic heterogeneity in GDM. Insulin secretion and resistance vary markedly among affected women and influence pregnancy outcomes, yet are not reflected by glucose measurements alone. C-peptide, produced equimolarly with insulin but less subject to hepatic clearance, serves as a reliable marker of endogenous insulin secretion. Incorporating dynamic C-peptide measurements during OGTT could thus provide deeper insight into GDM pathophysiology and aid risk stratification for personalized management.