Intravenous Nitroglycerin for External Cephalic Version A Randomized Controlled Trial Jennifer Hilton, MD, MSc, Bruce Allan, MD, PhD, Cheryl Swaby, RN, Raouf Wah, BA, MD, John Jarrell, MD, Stephen Wood, MD, MSc, Sue Ross, PhD, and Quynh Tran, MD OBJECTIVE: To estimate whether treatment with intra- venous nitroglycerin for uterine relaxation increases the chance of successful external cephalic version. METHODS: Two double-blind, randomized clinical trials were undertaken: one in nulliparous women and a sec- ond in multiparous women. Women presenting for ex- ternal cephalic version at term were eligible to partici- pate. The primary outcome was immediate success of external cephalic version. Other outcomes were presen- tation at delivery, cesarean delivery rate, and side effects and complications. Sample size calculations were based on a 100% increase in success of external cephalic version with a one-sided analysis and 0.05 (80% power). RESULT: In total, 126 women were recruited— 82 in the nulliparous trial and 44 in the multiparous trial. Seven patients did not have external cephalic version before delivery but were included in the analysis of success of external cephalic version. One patient was lost to follow- up. The external cephalic version success rate for nullip- arous patients was 24% (10 of 42) in patients who received nitroglycerin compared with 8% (3 of 40) in those who receive placebo (P.04, one-sided Fisher exact test, odds ratio 3.85, lower bound 1.22). In multip- arous patients, the external cephalic version success rate did not differ significantly between groups: 44% (10 of 23) in the nitroglycerin group compared with 43% (9 of 21) in the placebo group (P.60). CONCLUSION: Treatment with intravenous nitroglyc- erin increased the rate of successful external cephalic version in nulliparous, but not in multiparous, women. Treatment with intravenous nitroglycerin appeared to be safe, but our numbers were too small to rule out rare serious adverse effects. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov,www. clinicaltrials.gov, NCT00896311 and NCT00901758. (Obstet Gynecol 2009;114:560–7) LEVEL OF EVIDENCE: I B reech presentation complicates 3–5% of term pregnancies. Since the Term Breech Trial, the majority of fetuses presenting breech now are deliv- ered by cesarean owing to the increased risk of perinatal mortality and morbidity with vaginal breech delivery. 1 External cephalic version has a recognized role in decreasing breech presentation at term and subsequent cesarean delivery rates. 2,3 The success rate of external cephalic version at term varies between 20% and 80%. The success rate is higher in multiparous women and with the use of betamimetic agents (such as ritodrine) for tocolysis 2–10 . Ritodrine is no longer available in Canada, and the current Canadian standard of care is to conduct external cephalic version with no tocolysis. Nitroglyc- erin has been studied as an alternate uterine relaxant for use during external cephalic version. Sublingual nitroglycerin spray did not significantly improve ex- ternal cephalic version success rates compared with placebo in women who had failed a previous version attempt or in multiparous women. 2,11–13 Because intra- venous nitroglycerin action (90 seconds) and clear- ance (2–5 minutes) are faster compared with sublin- gual nitroglycerin, intravenous nitroglycerin allows From the Departments of Obstetrics and Gynecology, Community Health Sciences, and Family Medicine, University of Calgary, Calgary Health Region, Calgary, Alberta, Canada. Funded by a peer-reviewed grant from the Adult Research Committee, Calgary Health Region, Alberta, Canada. Presented at the Society of Obstetricians and Gynecologists of Canada Annual Meeting, June 25, 2007, Ottawa, Ontario, Canada. Corresponding author: Sue Ross, PhD, Department of Obstetrics and Gynaeco- logy, University of Calgary, 4th Floor, North Tower, Foothills Medical Centre, 1403 29 Street NW, Calgary, AB T2N 2T9, Canada; e-mail: sue.ross@ calgaryhealthregion.ca. Financial Disclosure The authors did not report any potential conflicts of interest. © 2009 by The American College of Obstetricians and Gynecologists. Published by Lippincott Williams & Wilkins. ISSN: 0029-7844/09 560 VOL. 114, NO. 3, SEPTEMBER 2009 OBSTETRICS & GYNECOLOGY