BACKGROUND: Learning Clubs is a multi-component intervention to address the eight common risk factors for women’s health, and infant’s health and development in resource-constrained settings. We are testing in a cluster randomized controlled trial in rural Vietnam whether this intervention improves cognitive development in children when they are aged two. There are few comprehensive process evaluations of complex interventions to optimise early childhood development. The aim is to conduct a planned process evaluation of the Learning Clubs intervention in Vietnam. METHODS: The evaluation will be conducted alongside the Learning Clubs trial using both qualitative and quantitative methods. Four domains will be included in the evaluation:  Context - how contextual factors affect the implementation and outcomes;  Implementation - what aspects of the Learning Clubs intervention are actually delivered and how well the intervention is delivered;  Mechanism of impact - how the intervention produces changes in the primary and secondary outcomes; and  National integration - how the intervention can be scaled up for application nationally. Purposive sampling will be used to recruit project stakeholders from commune, provincial and national levels. Results of the process evaluation will be integrated with those of the outcome and economic evaluations to provide a comprehensive picture of the effectiveness of the Learning Clubs intervention for early childhood development in rural Vietnam. DISCUSSION: Results of the evaluation will provide evidence about the implementation of the intervention and explanations for any differences in the outcomes between participants in intervention and control conditions. The evaluation will be integrated into each stage of the outcome assessments, but will be implemented by a bilingual team independent of the team implementing the intervention. It will therefore provide evidence which will not be influenced by or influence the intervention and will inform both generalisation to other settings and scalability in Vietnam. TRIAL REGISTRATION: Trial registration number ACTRN12617000442303 on the Australian New Zealand Clinical Trials Registry. Registered 27/03/2017. Prospectively registered.
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