3.3.3 Premature birth rate before 34 weeks
Eight studies were included for this analysis[9-15,17]. Given the significant heterogeneity across studies (P =0.08, I 2=45%), sensitivity analysis was performed to detect the source of heterogeneity. Fichera 2019 et al. was found to be the most influential study. After excluding this study, no significant heterogeneity was noted (P =0.58,I 2=0%), and a fixed-effect model was used for analysis. Results revealed that the premature birth rate before 34 weeks in the cervical pessary group was significantly lower than that in the cervical cerclage group (RR =0.68, 95%CI : 0.51 to 0.89,P <0.006). Sensitivity analyses did not significantly alter the results, suggesting that the results were predominantly stable (Figure 1-4).