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External cephalic version: success rates with and without nitrous oxide
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  • Thoa Ha,
  • Robyn Lamar,
  • Cinthia Blat,
  • Melissa Rosenstein
Thoa Ha
Emory University

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Robyn Lamar
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Cinthia Blat
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Melissa Rosenstein
University of California San Francisco
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Objective To compare the conversion rate of non-cephalic to cephalic presentation in external cephalic version (ECV) with and without nitrous oxide Design Retrospective cohort study Setting Single, tertiary care institution between January 2016 an June 2017 Population Women with singleton, term gestation ECVs identified via International Classification of Diseases Clinical Modification diagnosis code with breech or malpresentation. Pregnancies with preterm, multi-fetal gestation, abnormal placentation, and rupture of membranes were excluded Methods Logistic regression was performed to test whether nitrous oxide was associated with successful conversion to cephalic presentation. Main Outcomes The primary outcome was successful rate of conversion to cephalic presentation. The secondary outcome was the rate of vaginal delivery. Results During the study period, 167 women underwent ECV: 77 with nitrous oxide and 90 without nitrous oxide. Of the 77 women who used nitrous oxide, 25 (32.5%) were successful and 17 of these women delivered vaginally (68%). Of the women who underwent ECV without nitrous oxide, 29 (32.2%) successfully converted and 21 of these delivered vaginally (72%). After controlling for confounders, the use of nitrous oxide had no clinically or statistically significant difference on ECV success rates (OR 1.08, 95% CI 0.52-2.23). Conclusion Nitrous oxide does not seem to affect conversion rate to cephalic presentation in ECV. Further studies are needed to determine the impact of nitrous oxide on women’s decision to undergo ECV and on patient satisfaction and tolerability. Funding The authors received no financial support for the research, authorship, or publication of this data.