1. Department of Obstetrics , University Hospital Charité , Berlin , Germany
2. Department of Gynecology and Obstetrics , Vivantes Klinikum Im Friedrichshain , Berlin , Germany
3. Faculty of Medicine, Obstetrics and Gynecology , University Hospital Schleswig-Holstein , Kiel , Germany
4. Department of Gynecology and Obstetrics , Asklepios Kliniken Barmbek, Wandsbek und Nord-Heidberg , Hamburg , Germany
5. Asklepios Proresearch , Hamburg , Germany