1Department of Obstetrics, University Hospital of Zurich, Zurich, Switzerland
2Department of Obstetrics, University Hospital of Bern, Bern, Switzerland
3Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, Texas, USA
4Department of Obstetrics and Gynecology, Yale University School of Medicine New Haven, Connecticut USA
5University of Virginia, Charlottesville, Virginia, USA