1. Department of Public Health, Erasmus University Medical Center, Rotterdam, The Netherlands.
2. Department of Obstetrics and Gynaecology, Erasmus University Medical Center, Rotterdam, The Netherlands.
3. Department of Obstetrics, University Medical Center, Utrecht, The Netherlands.
4. Department of Obstetrics, Amphia Hospital, Breda, The Netherlands.
5. University Surgical Unit, Southampton, General Hospital, Southampton, United Kingdom.