Screening for Gestational Diabetes Mellitus (GDM) is controversial. This prospective study compared different sets of diagnostic cut-off points on plasma glucose measurements following a 75g Oral Glucose Tolerance Test (OGTT). Methods: Women who had maternal risk factors for GDM were recruited at their convenience at their first prenatal visit and consented to a one-step OGTT at 26-28 weeks gestation. All women fulfilling the World Health Organization (WHO) 2013 diagnostic criteria received standard care for GDM.