1. Department of Obstetrics and Gynaecology, Centre for Reproductive Medicine, Academic Medical Centre, Amsterdam, The Netherlands
2. Department of Epidemiology, Biostatistics and Bioinformatics, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
3. Department of Public Health, Academic Medical Centre, Amsterdam, The Netherlands
4. Department of Obstetrics and Gynaecology, St. Antonius Hospital, Nieuwegein, The Netherlands
5. Department of Obstetrics and Gynaecology, University Medical Centre Maastricht, Maastricht, The Netherlands
6. Department of Obstetrics and Gynaecology, Albert Schweitzer Hospital, Dordrecht, The Netherlands
7. Elisabeth Tweesteden Ziekenhuis, Centrum Voortplantingsgeneeskunde Brabant, Tilburg, The Netherlands
8. Department of Obstetrics and Gynaecology, Medical Centre Leeuwarden, Leeuwarden, The Netherlands
9. Department of Obstetrics and Gynaecology, Treant Zorggroep, locatie Scheper Hospital, Emmen, The Netherlands
10. Department of Obstetrics and Gynaecology, Spaarne Gasthuis, Haarlem, The Netherlands
11. Department of Obstetrics and Gynaecology, Maxima Medical Centre, Veldhoven, The Netherlands
12. Julius Centre for Health Sciences and Primary Care, University Medical Centre Utrecht, Utrecht, The Netherlands
13. School of Medicine, The Robinson Institute, University of Adelaide, Adelaide, Australia
14. The South Australian Health and Medical Research Institute, Adelaide, Australia