First-trimester fasting plasma glucose levels and progression to type 2 diabetes: A 5-year cohort study

Objective: Impaired fasting glucose is a prediabetic condition defined as glucose levels of 100–125 mg/dL and is considered a risk factor for type 2 diabetes. However, this definition does not confer to pregnancy. The significance of first-trimester fasting glucose and future progression to diabetes is not well defined. Therefore, we aimed to evaluate the progression to type 2 diabetes according to first- trimester fasting plasma glucose levels, as compared with gestational diabetes, a well-established risk factor for diabetes, in up to 5-year follow-up postpartum. Methods: A retrospective analysis of 69 001 parturients, evaluating fasting plasma glucose levels measured during the first trimester. The primary outcome was the incidence of type 2 diabetes within 5 years post-delivery. Fasting plasma glucose levels were categorized in 10 mg/dL increments. Receiver operating characteristic-area under the curve (ROC-AUC) statistics and the Youden index were employed to identify the optimal fasting plasma glucose cutoff for progression to type 2 diabetes. Survival analysis was applied to calculate the adjusted hazard ratios (aHRs) for type 2 diabetes progression with further stratification to maternal obesity status. Results: The identified fasting plasma glucose cutoff for progression to type 2 diabetes was 86.5 mg/dL. This cut-off demonstrated superior performance compared with gestational diabetes diagnosis. Stratification by maternal obesity revealed enhanced predictive capabilities for type 2 diabetes, particularly among patients without obesity. Conclusions: Increased first-trimester fasting plasma glucose levels are associated with progression to type 2 diabetes, at least as gestational diabetes. For patients without obesity, first-trimester fasting plasma glucose has a more pronounced impact on progression to diabetes.