Use and application of implementation science theories, models, and frameworks in maternal and child health research in South Asia: a systematic review protocol.

Background: Institutions responsible for implementing and conducting maternal and child health (MCH) programmes and projects in South Asia have accumulated substantial implementation experience across diverse health system contexts. Despite decades of experience, persistent challenges in intervention adoption, quality of delivery, equity of reach, and sustainability remain. Implementation science theories, models, and frameworks (TMFs) offer structured approaches to understand and address these challenges. However, global reviews have consistently found that TMFs are inconsistently selected, inadequately justified, inconsistently applied, and weakly linked to implementation strategies and outcomes. No regional synthesis has yet examined how TMFs are used in South Asian MCH research. Objectives: This protocol describes a methodological systematic review that will: (1) identify and characterise which implementation science TMFs are used in South Asian MCH research; (2) assess how explicitly and systematically TMFs are selected and applied across study phases; (3) examine whether researchers actively selected implementation strategies to address specific determinants, and to specify the mechanisms through which strategies are theorised to affect implementation outcomes; and (4) summarise gaps and opportunities to inform implementation research practice, including the selection of frameworks that are a good contextual fit relative to South Asian MCH settings. Methods: We will conduct a methodological systematic review with narrative and analytic synthesis. Eligible studies include primary empirical quantitative, qualitative, or mixed-methods studies focused on implementation, delivery, scale-up, process evaluation, or quality improvement of MCH interventions in programmatic settings of South Asia (India, Pakistan, Bangladesh, Nepal, Sri Lanka, Bhutan, Maldives, Afghanistan), published since January 2000. Studies will not be excluded based on explicit TMF use; TMF use will instead be treated as an object of analysis. Searches will be conducted across six databases, supplemented by grey literature searches. Screening and data extraction will be conducted independently by two reviewers using Covidence. TMF application will be appraised using criteria informed by the Systematic Evaluation and Selection of Implementation Science Theories, Models and Frameworks (SELECT-IT framework), and study quality will be assessed using the Mixed Methods Appraisal Tool (MMAT). Expected contribution: This review will produce the first region-specific synthesis of implementation science TMF use in South Asian MCH research. By systematically uncovering gaps in how previous MCH programme evaluations have applied implementation science frameworks, the review will improve the ability of researchers, implementers, and policymakers to identify key obstacles that limit successful and sustainable programme implementation in the region. Findings will provide methodological guidance to strengthen future implementation research practice and inform the development and contextual adaptation of implementation science frameworks better suited to South Asian MCH contexts. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/view/CRD420261345489, identifier CRD420261345489.