3 | RESULTS
3.1 | Study selection and characteristics of included studies
A total of 915 studies were obtained during the initial search. Subsequently, 371 duplicates were distinguished and excluded with  Endnote software. From the remaining 544 articles, 496 articles were exempted after scanning titles and abstracts. Finally, 35 articles were excluded after reading the full text, and 13 articles14-26 were included in the meta-analysis with a total of 1931 infants, including 964 in the MISA group and 967 in the control group.
The control groups in two articles 14,19 chose mechanical ventilation after intubation for surfactant delivery, whereas the intervention groups in 11 articles 15-18,20-26chose INSURE techniques. The MISA techniques used in the intervention groups were as follows: eight articles 14,16-20,22,26used LISA techniques, two articles 21,24 used MIST techniques, two articles 23,25 used both techniques, and one article 15 only mentioned administration of a surfactant via a thin catheter but did not specify which technique was used.
The application of cesarean sections and antenatal steroids was similar between the two groups in each study. All studies described similar criteria for surfactant delivery with similar values of fractional oxygen inhalation (FiO2) and/or respiratory distress severity, whereas 12 articles 14,16-26 described criteria for rescue intubation. In ten articles14-21,24,26, the type of pulmonary surfactant was Curosurf, whereas in three articles 22,23,25, three other kinds of pulmonary surfactant were used. The literature screening process is shown in Figure 1, and the basic characteristics of the included studies are given in Table 1.