Kangaroo Care as an intervention in randomised controlled trials in neonatal intensive care.

Kangaroo Care (KC) is an evidence-based intervention, with greatest benefit when initiated early and provided for continuous periods, as recommended by the World Health Organization. However, uncertainty remains around KC operationalisation in research settings and how this may influence subsequent implementation in routine practice. We conducted a narrative synthesis of KC intervention characteristics reported in randomised controlled trials (RCTs), based on a prior systematic review and meta-analysis. We focused on elements relevant to implementation, including instructions for delivery, recommended equipment or environment, initiation timing, duration of skin-to-skin contact, and contraindications. Our synthesis shows that, even within RCTs, KC is frequently not delivered in line with WHO recommendations with respect to initiation timing, duration, and eligibility. This contributes to uncertainty in clinical target setting and reflects an implementation gap that mirrors challenges observed in routine care. Commonly reported barriers included infrastructural constraints, staffing and training requirements, and cultural factors influencing caregiver participation. These findings highlight that evidence of KC effectiveness alone is insufficient to ensure optimal delivery in practice. Implementation studies conducted in real-life settings are needed to determine whether observed benefits translate into routine care and to identify strategies that support timely initiation, sufficient duration, and sustained KC provision. IMPACT: Key intervention characteristics of Kangaroo Care (KC), such as instructions, environment, initiation timing, duration, and contraindications that are often insufficiently reported in randomised controlled trials, but critical for implementation. Even in RCTs, KC is frequently not delivered in accordance with WHO recommendations, highlighting uncertainty in clinical target setting and revealing an implementation gap that extends beyond routine clinical practice into research settings. By identifying recurring infrastructural, personnel, and cultural barriers across trials, this work informs the design of real-world effectiveness and implementation studies, including the ongoing NeoDeco effectiveness-implementation trial.