Study design and participants
physical disabilities
We conducted a cluster randomized controlled trial (C-RCT) every two weeks from July to December 2019 in eight townships of Fenxi County, a poverty-stricken area in Shanxi Province of China [The intervention group participated in Care Group Intervention while also receiving child health care services included in the basic public health services (BPHS) package, while the control group received only the child health care services included in the BPHS package. We intended for the caregiver-child pairs in the intervention group to participate in 24 group-based sessions over 12 months between July 2019 to June 2020. However, due to the COVID-19 pandemic, the pairs in the intervention group were only able to participate in a maximum of 12 group-based sessions from July to December 2019. Since January 2020, we suspended the offline intervention for six months, and facilitators switched to sending age-appropriate messages and relative links of nurturing care and child health to caregivers via Wechat (a free mobile application for text and voice messaging communication service), to encourage them to keep practicing and maintain positive nurturing practices learned before.Recruited by the village doctors, children who were aged 6-18 months by July 1, 2019, and their primary caregivers were eligible for inclusion in the intervention group. Each primary caregiver signed the informed consent form after confirming they completely understood the content and information. Exclusion criteria for data analysis were: 1) children with physical disabilities; 2) multiple births (eg, twins, triplets); 3) premature babies; and 4) children living more than five kilometres from the intervention site.