摘要:Background Early childhood development (ECD) programmes can help address early disadvantages for the 43% of children younger than 5 years in low-income and middle-income countries who have compromised development. We aimed to test the effectiveness of two group-based delivery models for an integrated ECD responsive stimulation and nutrition education intervention using Kenya's network of community health volunteers. Methods We implemented a multi-arm, cluster-randomised community effectiveness trial in three rural subcounties across 60 villages (clusters) in western Kenya. Eligible participants were mothers or female primary caregivers aged 15 years or older with children aged 6–24 months at enrolment. If married or in established relationships, fathers or male caregivers aged 18 years or older were also eligible. Villages were randomly assigned (1:1:1) to one of three groups: group-only delivery with 16 fortnightly sessions; mixed delivery combining 12 group sessions with four home visits; and a comparison group. Villages in the intervention groups were randomly assigned (1:1) to invite or not invite fathers and male caregivers to participate. Households were surveyed at baseline and immediately post-intervention. Assessors were masked. Primary outcomes were child cognitive and language development (score on the Bayley Scales of Infant Development third edition), socioemotional development (score on the Wolke scale), and parental stimulation (Home Observation for Measurement of the Environment inventory). Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov , NCT03548558 . Findings Between Oct 1 and Nov 12, 2018, 1152 mother–child dyads were enrolled and randomly assigned (n=376 group-only intervention, n=400 mixed-delivery intervention, n=376 comparison group). At the 11-month endline survey (Aug 5–Oct 31, 2019), 1070 households were assessed for the primary outcomes (n=346 group only, n=373 mixed delivery, n=351 comparison). Children in group-only villages had higher cognitive (effect size 0·52 SD [95% CI 0·21–0·83]), receptive language (0·42 SD [0·08–0·77]), and socioemotional scores (0·23 SD [0·03–0·44]) than children in comparison villages at endline. Children in mixed-delivery villages had higher cognitive (0·34 SD [0·05–0·62]) and socioemotional scores (0·22 SD [0·05–0·38]) than children in comparison villages; there was no difference in language scores. Parental stimulation also improved for group-only (0·80 SD [0·49–1·11]) and mixed-delivery villages (0·77 SD [0·49–1·05]) compared with the villages in the comparison group. Including fathers in the intervention had no measurable effect on any of the primary outcomes. Interpretation Parenting interventions delivered by trained community health volunteers in mother–child groups can effectively promote child development in low-resource settings and have great potential for scalability. Funding Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health.