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

Abstract

Diagnosis of dysglycemia is traditionally based on classical criteria, such as those outlined by the American Diabetes Association (ADA), which rely on isolated glucose measurements. However, these static assessments may not fully capture an individual's dynamic glycemic profile. Continuous glucose monitoring (CGM) offers an alternative approach that provides a more comprehensive and accurate reflection of glycemic status over time. Women with a history of gestational diabetes mellitus (GDM) represent a particularly high-risk group. Compared with women who maintained normoglycemia during pregnancy, those with prior GDM have a significantly increased risk of developing dysglycemia. In addition to altered glucose metabolism, they frequently exhibit a cluster of cardiometabolic abnormalities, including obesity, dyslipidemia, hypertension, and early cardiac dysfunction. To compare continuous glucose monitoring to American Diabetes Association criteria, in the postpartum period in women who had developed gestational diabetes mellitus during their recent pregnancy, for diagnosis of type 2 diabetes mellitus complicated by clinical obesity. Between September 2023 and April 2025, we conducted a multiproposal cohort study at King's College Hospital, London, UK. We invited consecutive women with and without gestational diabetes mellitus at 5 months postpartum. Gestational diabetes mellitus patients were also invited for a 1-year follow-up clinic. Blinded continuous glucose monitoring (Dexcom G7; Dexcom, San Diego, CA) was performed for 10 days. The primary outcome was type 2 diabetes mellitus with clinical obesity, defined by first, the American Diabetes Association criteria (hemoglobin A1c ≥6.5%, fasting plasma glucose ≥126 mg/dL, or 2-hour oral glucose tolerance test of ≥200 mg/dL), and second, continuous glucose monitoring average glucose ≥131.5 mg/dL, which is the mean+2 standard deviation of our nongestational diabetes mellitus 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. We examined 1118 women, including 276 (24.7%) nongestational diabetes mellitus controls at 5 months postpartum, 539 (48.2%) postgestational diabetes mellitus at 5 months postpartum, and 303 (27.1%) postgestational diabetes mellitus at 1 year postpartum. In the nongestational diabetes mellitus group, the mean+2 standard deviation average glucose was ≥131.5 mg/dL. At 5 months postpartum in the gestational diabetes mellitus group, continuous glucose monitoring classified 8.9% (48/539) women as diabetes mellitus type 2 with clinical obesity and the respective value by the American Diabetes Association criteria was 4.3% (23/539). Women diagnosed by continuous glucose monitoring but not the American Diabetes Association criteria (n=35) had a worse cardiometabolic profile than those diagnosed by the American Diabetes Association criteria alone (n=10). Of the 35 additional cases, classified only by continuous glucose monitoring, 26 attended to the 1-year postnatal clinic and all still had an average glucose ≥131.5 mg/dL measured by continuous glucose monitoring and abnormal cardiometabolic profile. Postpartum follow-up in women who had gestational diabetes mellitus should not only focus on dysglycemia but also on their cardiometabolic profile. In this respect, continuous glucose monitoring is superior to American Diabetes Association criteria for diagnosis of diabetes mellitus type 2 with clinical obesity.