Effect of Entonox for pain management in labor: A systematic review and meta-analysis of randomized controlled trials

Entonox was one of the important methods for pain management in the delivery process. In previous years some studies have assessed the effect of this method in Iran. In this regard, the aim of this study was to systematically review studies addressing the effect of Entonox for pain management in labor. This systematic review and meta-analysis study was conducted in 2016. The required data was collected using keywords such as "Entonox", "nitrous oxide", "vaginal delivery", "pain relief", "obstetric", "labor pain", and "labor analgesia", from databases including Google scholar, PubMed, Science Direct, Magiran, SID, and Scopus, and hand-searching of related and valid journals and references of articles. Articles published from 2000 to 2016 were searched. To conduct meta-analysis, CMA:2 (Comprehensive Meta-analysis) was used. Finally, 14 articles were included in the study. Pain relief standard difference in mean between-groups was -1.01 (95% CI: -1.59 to -0.43, Q=148.5, df=8, p=0.02, I =76) this difference was significant (p