BACKGROUND: Italy, as many other developed Countries, is experiencing a deepening decline in birth rates, turning it into a structural issue that has led many Maternity Units to operate below the minimum delivery threshold. To ensure safe access to maternal healthcare, the 2010 State-Regions Agreement set a minimum target of 500 births per year for facility in areas with significant geographic challenges. OBJECTIVES: to describe the model developed by the Italian National Agency for Regional Healthcare Services (AgeNaS) which intend to assess accessibility to Maternity Units, considering both potential service areas and existing territorial coverage, and to allow for the simulation of network reconfiguration scenarios. DESIGN: a gravity model was adopted and tailored to the healthcare setting. The model is the Modified Three-Step Floating Catchment Area, divided into three stages: 1. calculation of access probability (using Huff's probability model)
2. estimation of the hospital bed capacity of the regional network of Maternity Units
3. calculation of an accessibility index for each area to the Maternity Unit network. To implement the gravity model, AgeNaS designed and developed a software application to process distance matrices based on road networks, which allow for accurate calculation of travel times and distances from municipalities to hospitals Results: the model highlights that activity data and territorial characteristics can redefine both current and potential future service areas, offering a transparent and replicable assessment. The potentiality of the AgeNaS model was demonstrated through a series of case studies: Montevarchi (Tuscany), Iglesias (Sardinia), and Orvieto (Umbria). CONCLUSIONS: the AgeNaS methodology is a valuable tool for regions and the central level, both applicable to the network of Maternity Units and to other territorial healthcare networks. This approach is flexible, adaptable, and can be standardized through known parameters, making it suitable for replicable analysis.