Continuous glucose monitoring: criteria for the diagnosis of type 2 diabetes mellitus with clinical obesity after gestational diabetes.

Abstract

OBJECTIVE To compare Continuous Glucose Monitoring (CGM) to American Diabetes Association (ADA) criteria, in the postpartum period in women who had developed gestational diabetes (GDM) during their recent pregnancy, for diagnosis of type 2 diabetes (DMT2) complicated by clinical obesity. STUDY DESIGN Between September 2023-April 2025, we conducted a multiproposal cohort study at King's College Hospital, London, UK. We invited consecutive women with and without GDM at 5-months postpartum. GDM patients were also invited for a 1-year follow-up clinic. Blinded CGM (Dexcom G7; Dexcom, San Diego, CA) was performed for 10 days. The primary outcome was T2DM with clinical obesity, defined by first, the ADA criteria (HbA1c ≥6.5%, FPG ≥126 mg/dL, or 2-hour OGTT of ≥200 mg/dL), and second, CGM average glucose ≥131.5 mg/dL, which is the mean + 2SD of our non-GDM group. Clinical obesity was defined by the recently published The Lancet Diabetes and Endocrinology Commission, as excess body fat directly affecting the function of organs and tissues. RESULTS We examined 1,118 women, including 276 (24.7%) non-GDM controls at 5- months postpartum, 539 (48.2%) post-GDM at 5-months postpartum and 303 (27.1%) post-GDM at 1-year postpartum. In the non-GDM group the mean + 2SDs average glucose was ≥131.5 mg/dL. At 5-months postpartum in the GDM group, CGM classified 8.9% (48/539) women as DMT2 with clinical obesity and the respective value by the ADA criteria was 4.3% (23/539). Women diagnosed by CGM but not the ADA criteria (n=35) had a worse cardiometabolic profile than those diagnosed by the ADA criteria alone (n=10). Out of the 35 additional cases, classified only by CGM, 26 attended to the 1-year postnatal clinic and all still had an average glucose ≥131.5 mg/dL measured by CGM and abnormal cardiometabolic profile. CONCLUSIONS Postpartum follow-up in women who had GDM should not only focus on dysglycemia but on their cardiometabolic profile. In this respect, CGM is superior to ADA criteria for diagnosis of DMT2 with clinical obesity.