Investing in Early Childhood Development (ECD) has the potential to yield significant economic and social benefits. However, ECD systems worldwide currently face challenges, particularly in providing equitable access for marginalized children. The COVID-19 pandemic has further highlighted these issues, potentially impacting children's well-being and learning outcomes. To address these challenges, new approaches are required that consider the complex and dynamic nature of ECD, with a focus on promoting equity and sustainability. Employing systems thinking is one promising approach that considers sociocultural and temporal variables, recognizing the need for a resilient infrastructure to support ECD ecosystem.

This narrative review supplements a recent mixed methods evidence review of the role of systems thinking funded by Porticus Philanthropic Entity and undertaken by the ECDAN, the Harvard T.H. Chan School of Public Health, and the Murdoch Children’s Research Institute. The report aims to describe complex systems initiatives implemented at scale in diverse settings. While a detailed complex adaptive systems analysis of these initiatives is beyond the scope of the report, initial descriptive analysis highlighting key features related to the implementation of complex systems initiatives and high-level reflections of cross-cutting elements are discussed.