Early Diagnosis of Gestational Diabetes Mellitus (EDoGDM) study: a protocol for a prospective, longitudinal cohort study

Introduction: A diagnosis of gestational diabetes mellitus (GDM) in low-risk pregnant women is based on an oral glucose tolerance test (OGTT) between 24 and 28 gestational weeks. However, there is insufficient evidence for why the test is performed in this time period. Moreover, the fetus may be exposed to hyperglycaemia prior to the current testing time frame, making earlier administration potentially advantageous. The main purpose of the present study is to investigate the GDM diagnostic value of an OGTT performed at 18-20 gestational weeks. The results of the study may provide scientific insight into the most beneficial time of OGTT for pregnant women. Methods and analysis: As a prospective, longitudinal cohort study, the Early Diagnosis of Gestational Diabetes Mellitus (EDoGDM) study will recruit 570 pregnant women who meet the inclusion and exclusion criteria outlined below. OGTTs will be performed between 18 and 20 gestational weeks (early OGTT) and 24-28 gestational weeks (regular OGTT). Clinical and laboratory information of the mother and their offspring will be collected for analysis. The prevalence of GDM at 18-20 gestational weeks will be described, and the sensitivity, specificity, positive predictive value and negative predictive value of early OGTT on diagnosis of GDM will be studied. Clinical outcomes associated with hyperglycaemia will be compared between groups diagnosed by early or regular OGTT. Ethics and dissemination: The study was approved by The Ethical Committees of The First Affiliated Hospital of Sun Yat-sen University (number 2016-042). Signed informed consent will be obtained from all participants. The results of this study will be disseminated in peer-reviewed journals.