1. Institute for Women’s Health, University College Hospital, 250 Euston Road, London NW1 6BU, UK
2. Department of Gynaecology, University Medical Centre Maribor, Ljubljanska 5, 2000 Maribor, Slovenia
3. Department of Obstetrics and Gynaecology, University Hospital Leuven, Herestraat 49, 3000 Leuven, Belgium
4. Department of Statistical Science, University College London, Gower Street, London WC1E 6BT, UK