Diagnosis of Gestational Diabetes

Abstract

Previous approaches to diagnosing gestational diabetes mellitus (GDM) have included 50 g, 75 g and 100 g glucose challenges, lasting 1-3 hours, with 1 or 2 elevations required. Thresholds were validated by their predictive value for subsequent diabetes, or were the same thresholds used in non-pregnant individuals. None were based on their prediction of adverse pregnancy outcomes. Diagnostic paradigms vary throughout the world, making comparisons impossible and severely limiting communication among investigators. The Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study collected outcome data on > 23,000 pregnancies recruited prospectively in nine countries after a blinded 75 g, 2-hour oral glucose tolerance test (OGTT) at 24-28 weeks gestation. Primary outcomes (LGA, PCS, neonatal hypoglycemia, high cord C-peptide), and most secondary outcomes (e.g. preeclampsia, preterm birth, shoulder dystocia and birth injury), were significantly, directly and continuously related to each of the three plasma glucose measurements. The International Association of Diabetes in Pregnancy Study Groups (IADPSG) developed recommendations for the use of a 75 g, 2-h OGTT, ≥ 1 elevation diagnosing GDM, with thresholds: fasting plasma glucose ≥ 5.1 mmol/L (92 mg/dL) , 1 h ≥ 10 mmol/L (180 mg/dL) and 2 h ≥ 8.5 mmol/L (153 mg/dL). These have generated wide discussion and are currently being considered throughout the world. They are pregnancy outcome-based; the 75 g glucose load will bring consistency to GTTs; universal adoption will lead to consistency of diagnostic criteria worldwide; studies of treatment at similarly mild levels of glycemia have demonstrated improvement in outcomes; use of a single abnormal value will obviate the confusion arising when one elevated value is encountered. The primary argument against the recommendations is that prevalence of GDM will rise to 16-18 %, increasing health care costs. Balanced against this is the world-wide epidemic of obesity, prediabetes and diabetes. © 2014 Informa Healthcare.