Evaluation of the Efficacy and Safety of an Equimolar Mixture of Oxygen and Nitrous Oxide in External Cephalic Version (ECV)

The variety of breech presentation at term is about 3-4% of all births. Our study aims to assess the value of using an equimolar mixture of oxygen and nitrous oxide. Indeed, in some patients algic or relaxed, the success rate seems more important. It's a single blind prospective randomized controlled study, comparing success rate of ECV after an equimolar mixture of oxygen and nitrous oxide or placebo (medical air). We need to include 150 patients (75 in each arm), for a period of 2 years. After ECV, we will give the patient a satisfaction questionnaire. We compare the success rate of ECV as primary outcome.