1. Department of Obstetrics and Gynecology OLVG Amsterdam the Netherlands
2. Department of Obstetrics and Gynecology Martini Hospital Groningen the Netherlands
3. Beval Beter Amsterdam the Netherlands
4. Department of Quality and Safety St. Antoniusziekenhuis Nieuwegein the Netherlands
5. Department of Research and Epidemiology OLVG Amsterdam the Netherlands
6. Academic Center for Dentistry Amsterdam (ACTA) University of Amsterdam and VU University Amsterdam Amsterdam the Netherlands
7. Institute of Health and Society University of Worcester Worcester UK