1. Institute of Anesthesiology, University Hospital Zurich, CH-8091 Zurich, Switzerland
2. Department of Cranio-Maxillofacial Surgery, University Hospital Zurich, CH-8091 Zurich, Switzerland
3. Department of Obstetrics and Gynecology, Division of Obstetrics and Perinatal Physiology, University Hospital Zurich, CH-8091 Zurich, Switzerland