1. Department of Obstetrics and Gynaecology, Justus-Liebig-University Giessen, Giessen, Germany.
2. Ludwig Maximilian Universität München, Munich, Germany.
3. Department of Gynaecology and Gynaecological Endocrinology and Oncology, Philipps University, Marburg, Germany.
4. Institute of Quality Assurance, Eschborn, Germany.