Metabolic recovery at 12 months postpartum among individuals with glucose intolerance in pregnancy

Background: Gestational diabetes mellitus (GDM) is associated with long-term risk for maternal Type II Diabetes (T2DM). We evaluated β-cell function during pregnancy and at 12 months postpartum in individuals with varying levels of glucose intolerance in pregnancy. Methods: This is a planned follow-up to the Gestational Diabetes Diagnostic Methods (GDM2) trial, which randomized pregnant individuals to either a 75-gram oral glucose tolerance test (OGTT) with GDM diagnosed with ≥1 abnormal value per IADPSG guidelines, or a 100g OGTT with GDM diagnosed with ≥2 abnormal values per Carpenter-Coustan (CC) criteria. All participants with treated GDM, those with untreated mild glucose intolerance (MGI, one abnormal value on CC criteria), and half of participants with normal glucose tolerance were invited for a follow-up visit at 12 months postpartum where they underwent a 75g OGTT measuring insulin and glucose at all time points. Measures assessed included Stumvoll, Matsuda, and Disposition Indices and other metabolic factors to evaluate insulin sensitivity, resistance, and β-cell function. Results: In pregnancy and 12-month postpartum visits, the disposition and Matsuda indices demonstrated significantly more insulin resistance among those with MGI and GDM compared to those without GDM (41.0±41.6, 28.7±26.6, 20.0±15.9, p<0.001), whereas the Stumvoll index was similar among groups. The rate of change from pregnancy to postpartum in both the Matsuda and Stumvoll indices were similar across the three groups, indicating individuals were likely returning to their baseline levels of glucose tolerance rather than recovering from a pregnancy-specific metabolic impairment. Although this study was underpowered for this outcome, there was a trend towards higher rates of prediabetes and T2DM in those with MGI and GDM (14.6%, 25.5%, 24%, p=0.09). Conclusions: Patients with MGI have significant impairments in insulin resistance similar to individuals with treated GDM one year postpartum and should receive follow-up for potential progression to T2DM.