1. Obstetrics and Gynecology, Mathias-Spital Rheine, Frankenburgstraße 31, 48431 Rheine, Germany
2. Obstetrics and Gynecology, St. Franziskus Hospital, Hohenzollernring 72, 48145 Münster, Germany
3. Clinic of Obstetrics and Gynecology, University Hospital of Udine, University of Udine, P.le S. M. Della Misericordia 1, 35100 Udine, Italy
4. Clinic of Obstetrics and Gynecology, University of Münster, Albert-Schweitzer Campus 1, 48149 Münster, Germany