Gao 2015.

Methods	Randomized Controlled Trial
Participants	80 preterm infants (75 in analysis) (27 to 37 weeks GA); 2 groups – skin‐to‐skin, incubator control Postnatal age ‐ N/A Birth weight, mean (SD N/A), g: 2017.8 (skin‐to‐skin); 2030 (incubator) Painful procedure: heel lance Study period: unclear
Interventions	First heel lance: both groups in incubator Next three heel lances: Treatment: Skin‐to‐skin: 30 minutes pre‐procedure Control: Prone in incubator: 30 minutes pre‐procedure
Outcomes	Crying time (seconds), grimacing time (seconds), heart rate
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The authors report that they randomly assigned the infants in the study to either the KMC or incubator condition using a "random table format". This statement does not provide enough information about the randomisation sequence and how it was generated and therefore has an unclear risk of bias.
Allocation concealment (selection bias)	Unclear risk	The authors report that they used a random table format to assign the infants in the study to the intervention conditions; however, they do not provide information regarding who had access to that table, who completed the randomisation, and any steps that were taken to conceal the allocation
Blinding (performance bias and detection bias) All outcomes	Low risk	Recordings were assessed by blind reviewers. Camera was focused on face with little surrounding area with no sound, low colour.
Incomplete outcome data (attrition bias) All outcomes	Low risk	The authors had some loss to follow‐up, but they provide rationale for the reasons that participants were lost, making this low risk of bias
Selective reporting (reporting bias)	Low risk	The authors report on all outcomes and provide complete within‐ and between‐group analyses to show differences between groups and across time.
Other bias	Low risk	There does not appear to be concerning issues related to other sources of bias. The authors provide detailed descriptions of how inter‐ and intra‐rater reliability were maintained for the behavioural outcomes reported.