Table 2

Risk of bias assessments

Study	Random sequence generation	Allocation concealment	Blinding of participant and personnel	Blinding of outcome assessment	Incomplete outcome data	Selective reporting	Other biases
Göpel et al27	Low risk	Low risk	High risk	High risk	Low risk	Low risk	Criteria for providing surfactant were not similar across the two groups
Kanmaz et al28	Unclear	Low risk	High risk	High risk	Low risk	Low risk
Mirnia et al29	Unclear	Unclear	High risk	High risk	Low risk	Unclear*
Bao et al30	Low risk	Unclear	High risk	High risk	Low risk	Unclear†	Trial stopped early
Mohammadizadeh et al31	Unclear	Low risk	High risk	High risk	Low risk	High‡
Kribs et al32	Low risk	Low risk	High risk	High risk	Low risk	Low risk

*Trial protocol not registered in a public trial registry.
†Trial protocol registered after completion of the study.
‡Outcomes of common neonatal morbidities, that is, NEC, ROP and PDA requiring treatment not provided.
NEC, necrotising enterocolitis; PDA, patent ductus arteriosus; ROP, retinopathy of prematurity.