Effect of nitrous oxide use on external cephalic version success rate; A systematic review and meta-analysis

Background Several adjuvant interventions have been evaluated for improving the success rate of external cephalic version (ECV) and reduce the rate of cesarean delivery (CD). Evidence regarding the effect of Nitrous oxide (NO) is limited with inconsistent results on pain score and success rate. Objective To examine the effect of inhaled NO on the success rate and pain score for women undergoing ECV. Search strategy MEDLINE, EMBASE, PubMed, Ovid Medline, ClinicalTrials.gov, the Cochrane Library and Google Scholars from inception till June 2020. Selection criteria Peer-review studies that examined the success rate of inhaled NO use during ECV attempt compared with or without the use of other analgesic agents were eligible for inclusion. Data collection and analysis All ascertained records were screened independently for eligibility by two authors. The study quality scores were evaluated as a source of heterogeneity by fitting meta-regression models to the individual study effect sizes. Results Of the 186 records, two randomized trials and one prospective cohort study (434 in the NO group and 286 in the controls) were deemed adequate for meta-analysis. ECV success rate did not differ significantly between the NO and the controls group (p=0.825; OR 1.036; 95% CI, 0.756-1.419). In addition, the use of NO did not affect pain scores (p=0.457; OR 0.759; 95% CI, -1.240-2.759) and there was no difference in the incidence of CD (p=0.943; OR 1.013; 95% CI, 0.703-1.46). Conclusion Use of NO during ECV is not associated with increase in ECV success rate and does not affect pain score.