1. Department of Obstetrics and Gynaecology, University Medical Centre Würzburg, Würzburg, Germany.
2. Department of Gynaecology and Obstetrics, Hospital Memmingen, Memmingen, Germany.
3. Department of Gynaecology and Obstetrics, Hospital Kempten, Kempten, Germany.
4. Department of Gynaecology and Obstetrics, University Medical Centre Ulm, Ulm, Germany.
5. Institute of Medical Biostatistics, Epidemiology and Informatics, University Medical Centre Mainz, Mainz, Germany.