1. Research Unit of Obstetrics and Gynecology, University of Southern Denmark, Odense, Denmark
2. Department of Clinical Research, University of Southern Denmark, Odense, Denmark
3. Clinic of Orthopaedic Surgery, University of Southern Denmark, Odense, Denmark
4. Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
5. Department of Clinical Epidemiology, Aarhus Universitet, Aarhus, Denmark
6. Department of Public Health, Aarhus Universitet, Aarhus, Denmark