ObjectiveTo evaluate burden of postpartum diabetes and other cardiometabolic risk factors among women who test positive for gestational diabetes mellitus (GDM) by International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria, but negative by alternate criteria. MethodsThis prospective cross-sectional study was conducted from 2019 to 2022 and is a sub-study of the CHIP–F cohort (Cohort Study of Indian Women with Hyperglycemia in Pregnancy and their Families). ResultsStudy participants (n = 826; 183 with normoglycemia and 643 with GDM using IADPSG criteria) were evaluated at a median (IQR) postpartum interval of 31 (21–45) months. Using the United Kingdom National Institute of Health and Care Excellence (UK NICE), Canadian Diabetes Association (CDA), and Diabetes in Pregnancy Study Group India (DIPSI) criteria, 251 (39.0 %), 148 (23.0 %) and 384 (59.7 %) women who tested positive for GDM by IADPSG criteria, would have tested negative. The incidence of postpartum diabetes among such women was 30.4, 34.3, and 48.2 per 1000 women-years, respectively, which was significantly higher than those testing negative by both IADPSG and UK NICE (5.0 per 1000 women-years), IADPSG and CDA (9.2/1000 women-years) and IADPSG and DIPSI criteria (5.0/1000 women-years). The burden of obesity and metabolic syndrome was also significantly higher in such women. ConclusionsWe found a significant burden of postpartum diabetes and cardiometabolic risk factors among women who tested positive for GDM by IADPSG, but negative by alternate criteria. There are potential clinical implications of a “failed” diagnosis for future cardiometabolic diseases that need to be carefully examined.