The new International Association of Diabetes and Pregnancy Study Groups (IADPSG) diagnostic criteria have been predicted to increase the prevalence of gestational diabetes mellitus 2-to-3 fold and will have important resource implications for healthcare systems. A bottom-up, prevalence-based analysis was undertaken to estimate the costs of universal screening for gestational diabetes mellitus in Ireland using the new criteria. Healthcare activity was identified from the Atlantic Diabetes in Pregnancy database and grouped into five categories: (i) screening and testing, (ii) GDM treatment, (iii) prenatal care, (iv) delivery care, and (v) neonatal care. When individual resource components were valued using unit cost data and aggregated, the total healthcare cost was estimated at Euro 46,311,301 (95% CI: Euro 36,381,038, Euro 68,007,432). The average cost per case detected was Euro 351 (95% CI: (Euro 126, Euro 558) and the average total cost per case detected and treated was Euro 9,325 (95% CI: Euro 5,982, Euro 13,996). Further research is required to determine the cost effectiveness of screening in the region with a view to improving resource allocation in this area in the future.