Oral Concurrent Session 2 – Diabetes

Objective: To evaluate hemoglobin A1c (A1c) and other shorterterm glycemic markers as predictors of gestational diabetes (GDM) and large for gestational age birthweight (LGA). Study Design:In a prespecified secondary analysis of a prospective cohort study at 9 US centers, we measured A1c, glycated albumin, and 1,5-anhydroglucitol at 10-14 weeks' gestation in gravidas with singleton pregnancies and no pre-existing diabetes.Outcomes were GDM at 24-28 weeks' gestation (Carpenter-Coustan criteria) and LGA (birthweight > 90%).We developed predictive models using glycemic markers and clinical factors (age, BMI, and history of GDM or macrosomia) in training data from 4 centers, with validation in data from the remaining 5 centers.We selected optimal thresholds for glycemic markers in combination with clinical factors by maximizing area under the ROC curve in logistic regression models.We then calculated the positive predictive value (PPV) at a pre-specified negative predictive value (NPV) threshold and prevalence (8.3% for GDM, 10% for LGA, based on US national data) to assess clinical utility of models for identifying at-risk individuals in early pregnancy.We compared PPVs from models with glycemic markers and clinical factors to those from models with clinical factors alone.Results: Among 2178 participants, 15.4% were diagnosed with GDM and 11.3% had LGA infants.No glycemic marker improved prediction of GDM or LGA compared to clinical factors alone (Figure).For prediction of GDM, PPV for the clinical model was 12.2% at NPV of 96% and 8.3% prevalence.The PPVs at the same NPV for glycemic markers ranged from 12.5-14.5%(Table ).For prediction of LGA, PPV for the clinical model was 12.4% at NPV of 95% and 10% prevalence.The PPVs at the same NPVs for glycemic markers ranged from 13.2-16.7%(Table).In validation, there was no significant difference between PPVs of models with glycemic markers versus those with clinical factors alone.Conclusion: Neither HbA1c nor other shorter-term glycemic markers at 10-14 weeks' gestation improved prediction of GDM or LGA beyond clinical factors alone.