Comparison of Tocolytic Agents for Successful External Cephalic Version: A Bayesian Network Meta-Analysis of Sixteen Randomized Controlled Trials

Background: Cesarean section is frequently performed for breech presentation; however, external cephalic version (ECV) is recommended as an alternative strategy to increase the likelihood of vaginal birth. Tocolytic agents are commonly administrated to improve ECV success, yet the comparative effectiveness of different regimens remains inadequately characterized. Aims: To systematically evaluate and compare the efficacy and safety of various tocolytic agents in facilitating successful ECV through a Bayesian network meta-analysis. Study Design: Bayesian network meta-analysis. Methods: Bayesian network meta-analysis was performed using the "gemtc" package in R 4.1.1. Treatment effects were quantified by calculating odds ratios (ORs) with corresponding 95% credible intervals (CrIs). Surface under the cumulative ranking curve values were used to rank tocolytic agents according to ECV success rates, maternal outcomes, and adverse events. Results: A total of sixteen RCTs encompassing 2,817 participants and six distinct tocolytic agents met the inclusion criteria. Compared with placebo, terbutaline (OR: 2.7, 95% CrI: 1.1-6.4) and ritodrine (OR: 2.2, 95% CrI: 1.4-3.9) were associated with significantly higher ECV success rates. Additionally, terbutaline was linked to an increased likelihood of vaginal delivery (OR: 2.0, 95% CrI: 1.0-2.9). Maternal adverse effects, including tachycardia, palpitations, hypotension, nausea, dizziness, and flushing, were more frequently reported with terbutaline, nifedipine, and nitroglycerin than with placebo. No statistically significant differences in fetal heart rate abnormalities were detected among the elevated interventions. Conclusion: Terbutaline and ritodrine appear to offer superior efficacy in improving ECV success compared with alternative tocolytic agents, albeit with a higher incidence of maternal side effects. Consequently, clinical decision-making regarding tocolytic use should be informed by a comprehensive assessment of the associated benefits and potential risks.