1. Department of Obstetrics and Gynaecology; VU University Medical Center; Amsterdam The Netherlands
2. Department of Obstetrics and Gynaecology; Deventer Hospital; Deventer The Netherlands
3. Obstetrics and Gynaecology Unit; Queen Charlotte's and Chelsea Hospital, Imperial College London; UK
4. Department of Obstetrics and Gynaecology; St Antonius Hospital; Nieuwegein The Netherlands
5. Department of Obstetrics and Gynaecology; University Hospitals Katholieke Universiteit Leuven; Leuven Belgium