Results  
The electronic database search revealed a total of 9032 studies. After screening for suitability, 34 studies were included in the final synthesis 23-56. The PRISMA flow diagram is depicted in Figure 1 . Thirty-three studies (3994 neonates) and 31 studies (3783 neonates) were analysed for the primary outcomes of treatment failure and requirement of mechanical ventilation, respectively. The mean gestational age of the neonates was 31 weeks (E-Figure 1). Five studies had enrolled neonates who had already received surfactant prior to randomisation. The time cuts-offs for treatment failure and mechanical ventilation was within the first 72 hours after randomisation for most of the included studies. The characteristics of the included studies are given in Table 1 .