Antenatal A1C, Postpartum Abnormal Glucose Tolerance, and Large for Gestational Age Infants in a Multi-ethnic Cohort of Women with Gestational Diabetes

Introduction: Gestational diabetes (GDM) is a risk factor for type 2 diabetes and delivery of a large for gestational age (LGA) or macrosomic infant.;Objective: The primary objectives of this study were to analyze the association of A1C at GDM diagnosis with postpartum abnormal glucose and with risk of macrosomia or LGA. The secondary objective was to determine if, among overweight or obese women with gestational diabetes (GDM), weight loss after GDM diagnosis is associated with lower birth weight.;Methods: Women with singleton pregnancies managed for GDM at the Carolinas Medical Center Diabetes and Pregnancy Program between November 2000 and April 2011 were eligible for this retrospective cohort study. Clinical information including maternal pre-pregnancy body mass index, A1C at GDM diagnosis, treatment, and medical and obstetric history was abstracted from medical records. A parametric survival model was used to assess the association of A1C at GDM diagnosis with postpartum maternal impaired fasting glucose (IFG) and impaired glucose tolerance (IGT). Logistic regression was used to analyze the association of A1C at GDM diagnosis with risk of LGA or macrosomia. The association of weight loss after GDM diagnosis and birth weight was analyzed using linear regression stratified by maternal pre-pregnancy overweight or obesity class (I, II/III).;Results: After adjustment, there was a trend of increased risk of postpartum abnormal glucose across increasing quartiles of A1C (p for trend <0.001). After adjustment, there was no detectable trend of increased risk for LGA (p for trend=0.12) or macrosomia (p for trend=0.20) across increasing quartiles of A1C at GDM diagnosis. After adjustment, weight loss was associated with 241 g lower mean birth weight among overweight women (95% CI -394.66, -87.32), and 117 g lower mean birth weight among obese I women (95% CI -328.63, 95.31), but among obese II/III women weight loss after GDM diagnosis was not associated with birth weight (p=0.81).;Conclusion: A1C may be a useful tool for identifying GDM patients at highest risk of developing postpartum abnormal glucose, but may not be linearly associated with LGA or macrosomia, due to the mediating effect of glycemic control in this well-controlled clinical setting.