1. Department of Reproductive Medicine and Gynaecology, University Medical Centre Utrecht, Utrecht University, PO Box 85500, 3508 GA Utrecht, The Netherlands
2. Julius Centre for Health Sciences and Primary Care, University Medical Centre Utrecht, Utrecht University, PO Box 85500, 3508 GA Utrecht, The Netherlands
3. Department of Obstetrics and Gynaecology, Maxima Medical Centre Veldhoven, PO Box 7777, 5500 MB Veldhoven, The Netherlands
4. Department of Obstetrics and Gynaecology, Onze Lieve Vrouwe Gasthuis Oost, PO Box 95500, 1190 HM Amsterdam, The Netherlands
5. Department of Reproductive Medicine, Rijnstate Hospital, PO Box 9555, 6800 TA Arnhem, The Netherlands
6. Department of Obstetrics and Gynaecology, Gelre Hospital, PO Box 9014, 7300 DS Apeldoorn, The Netherlands
7. Department of Obstetrics and Gynaecology, Diakonessenhuis, PO Box 80250, 3508 TG Utrecht, The Netherlands
8. Department of Obstetrics and Gynaecology, Catharina Ziekenhuis, PO Box 1350, 5602 ZA Eindhoven, The Netherlands
9. Department of Obstetrics and Gynaecology, University Hospital Gent, 9000 Gent, Belgium
10. Department of Gynaecology, Wilhelmina Hospital, PO Box 30001, 9400 RA Assen, The Netherlands
11. Department of Gynaecology, Maasstad Hospital, PO Box 9100, 3007 AC Rotterdam, The Netherlands
12. Department of Epidemiology, University of Groningen, University Medical Centre Groningen, PO Box 30.001, 9700 RB Groningen, The Netherlands
13. Department of Obstetrics and Gynaecology, Erasmus Medical Centre, Postbus 2040, 3000 CA Rotterdam, The Netherlands
14. The Robinson Research Institute, School of Paediatrics and Reproductive Health, University of Adelaide, SA 5006 Adelaide, Australia
15. The South Australian Health and Medical Research Unit, PO Box 11060, SA 5001 Adelaide, Australia