1. Department for Gynecology, Obstetrics and Reproductive Medicine, University of Witten/Herdecke, Witten, Germany

2. Department for Gynecology, Obstetrics and Reproductive Medicine, Saarland University Hospital, Homburg, Germany

3. Department of Obstetrics and Gynecology, Rheinlandklinikum Dormagen, Dormagen, Germany

4. Media Park Clinic, Cologne, Germany

5. Institute of Pathology, Grevenbroich, Germany

6. Institute for Medical Statistics and Epidemiology, University of Cologne, Germany