Methods
We conducted a cluster (township) randomized controlled trial (C-RCT) every two weeks from July 2019 to June 2020 in a poverty-stricken area located in Shanxi, China. The outbreak of the COVID-19 pandemic suspended the implementation of the intervention in January 2020. The caregiver-child pairs in the intervention group participated in 12 group-based sessions with a structured curriculum and learning materials emphasizing nurturing ability and early childhood development. We applied a difference-in-differences (DID) model to estimate the intervention’s impact. The analysis follows the intention-to-treat (ITT) principle. We used standard economic costing methods to estimate the cost of implementing the Care Group over the intervention period and adopted a societal perspective in the analysis.