Controversy remains surrounding International Association of Diabetes and Pregnancy Study Group (IADPSG) diagnostic criteria for gestational diabetes mellitus (GDM), including perceived improvement in perinatal outcomes and health service implications. We compared perinatal outcomes for untreated women meeting IADPSG‐only criteria and women without GDM in Victoria. Women meeting IADPSG‐only criteria were characterised according to fasting and one hour glucose thresholds and by region of birth. IADPSG criteria identified women with increased risk of adverse perinatal outcomes, particularly women born in Australia compared to Asian regions.