Seven RCTs (total n=2,354) were included.
No statistical heterogeneity between the studies was observed. However, the authors stated that there were considerable differences in the characteristics and the quality of the studies, which made a meta-analysis inappropriate. These differences were further explored graphically using forest plots.
The authors stated that, overall, the differences in the quality of the studies did not have a large effect on the pooled summary estimate. The pooled estimates for a reduction in spontaneous pre-term birth before 34 and 37 weeks were OR 0.75 (95% confidence interval, CI: 0.59, 0.96) and OR 0.86 (95% CI: 0.71, 1.05), respectively. In the four studies that reported on adverse events, perinatal death, ruptured membranes, chorioamnionitis and puerperal pyrexia were more common in patients receiving cervical cerclage than in the controls.