BackgroundIn Pakistan, high prevalence of delays in early child development (ECD) is associated with poverty and lack of mothers’ caregiving skills. GP clinics, the main sources of care in poor urban localities, lack quality ECD care delivery. A contextualised intervention was developed and tested to enable GPs to deliver clinic-based, tool-assisted ECD counselling of mothers on a quarterly basis.AimTo assess the effectiveness of delivering a contextualised ECD mother-counselling intervention.Design & settingClustered randomised controlled trial, in poor urban localities of Pakistan. Locality clusters were allocated to intervention and control arm using simple randomisation.MethodA total of 2327 mother–child pairs were recruited at 32 GP clinics, one from each cluster-locality; 16 GP clinics per arm. The clinic-based counselling intervention covering child stimulation, nutrition, and maternal mental health was delivered mainly by clinic assistants to mothers at ≤6 weeks, and 3, 6, and 9 months of child age. At 12 months of child age, each mother–child pair was assessed for the primary outcome, that is, delays in the five development domains (determined by Ages and Stages Questionnaire-3 [ASQ-3] score); and secondary outcomes, namely the prevalence of stunting and maternal depression (determined by Patient Health Questionnaire-9 [PHQ-9] score). The outcome assessors were blinded to the cluster–arm allocation. Outcome analyses were calculated on cluster-level.ResultsAt 12 months, the number of children with delay in two or more development domains was significantly lower in the intervention arm (-0.17 [95% confidence interval {CI} = -0.26 to -0.09]; P<0.001) compared to the control arm. The difference in the prevalence of child stunting and maternal depression were also significant at -0.21% (95% CI = -0.30 to -0.13; P<0.001) and -0.23% (95% CI = -0.29 to -0.18; P = 0.000) respectively.ConclusionContextualised ECD care, when delivered at GP clinics in poor urban localities, can effectively reduce the developmental delays during the first 12 months of the child's life.