1. Department of Obstetrics and Gynaecology; Academic Medical Center; Amsterdam; The Netherlands
2. Department of Clinical Epidemiology, Biostatistics and Bioinformatics; Academic Medical Center; Amsterdam; The Netherlands
3. St George's Healthcare NHS Trust; Department of Obstetrics and Gynaecology; London; UK
4. Hospital de Cabuenes; Department of Obstetrics and Gynaecology; Gijon; Spain
5. Jichi Medical University School of Medicine; Department of Obstetrics and Gynecology; Shimotsuke-shi; Tochigi-ken; Japan
6. VU University Medical Center; Department of Obstetrics and Gynaecology; Amsterdam; The Netherlands
7. University of Dundee; Division of Clinical & Population Sciences & Education, Academic Clinical Practice; Ninewells Hospital & Medical School; Dundee; UK
8. Zagazig Faculty of Medicine; Department of Obstetrics and Gynaecology; Zagazig, Ash Sharqiyah; Egypt