1. Department of Obstetrics and Gynaecology; Academic Medical Centre; Amsterdam the Netherlands
2. Department of Obstetrics and Gynaecology; Maastricht University Medical Centre; Maastricht the Netherlands
3. Department of Obstetrics and Gynaecology; Erasmus Medical Centre; Rotterdam the Netherlands
4. Department of Obstetrics and Gynaecology; Maxima Medical Centre; Veldhoven the Netherlands
5. Department of Public Health; Academic Medical Centre; Amsterdam the Netherlands
6. Department of Obstetrics and Gynaecology; Twee Steden Hospital; Tilburg the Netherlands
7. Department of Obstetrics and Gynaecology; Deventer hospital; Deventer the Netherlands
8. Department of Obstetrics and Gynaecology; Rijnstate hospital; Arnhem the Netherlands
9. Department of Obstetrics and Gynaecology; Albert Schweitzer Hospital; Dordrecht the Netherlands
10. Department of Obstetrics and Gynaecology; Medical Spectrum Twente; Enschede the Netherlands
11. Department of Obstetrics and Gynaecology; St. Antonius Hospital; Nieuwegein the Netherlands
12. Department of Obstetrics and Gynaecology; Sint Franciscus Gasthuis; Rotterdam the Netherlands
13. Department of Obstetrics and Gynaecology; Onze Lieve Vrouwe Gasthuis; Amsterdam the Netherlands
14. Department of Obstetrics and Gynaecology; VU University Medical Centre; Amsterdam the Netherlands
15. Clinical Research Unit; Academic Medical Centre; Amsterdam the Netherlands
16. The Robinson Research Institute; School of Paediatrics and Reproductive Health; University of Adelaide; Adelaide SA Australia