IMPACT DIABETES B2B will demonstrate the real-world implementation of an evidence-based, low-resource system-level intervention for healthy gestational weight gain and early prevention of maternal and child diabetes, overweight and obesity when delivered ‘at scale’ across antenatal settings. Gestational diabetes affects up to 18% of pregnancies worldwide and is an increasing health problem for both mothers and babies. By identifying those most at risk of developing gestational diabetes and working with them through personalised health coaching delivered via smartphone App, this project will engage, motivate and empower this target group to lead healthier lives for improved wellbeing and pregnancy outcomes. This project will demonstrate implementation within 3 European countries and Australia with clear line-of-sight on future scale-up across different contexts and resource settings via its innovative implementation toolkit and workshops for dissemination and exploitation. Pregnancy is a unique time in life with potential to influence maternal health, and the health of the next generation. IMPACT DIABETES B2B delivers breakthrough research in nutrition, exercise and behaviour change leading to an implementable low-resource system-level intervention. The personalised feedback will empower women to manage their health, delivering cost-effective management of excess gestational and post-pregnancy weight gain to: improve pregnancy and postpartum outcomes; improve utilisation of healthcare services; and encourage ongoing maternal health with sustainable impact for mother and family. Expertise in implementation science, lifestyle change, health psychology, mHealth technology, health economics and health service delivery will lead this mixed methods project. The project will co-design the intervention system, with end-user context and management explored throughout. The work will evaluate clinical, economic and implementation outcomes to inform future practice and policy.