1. Department of Obstetrics and Gynecology, University Medical Centre Groningen University of Groningen Groningen The Netherlands
2. Department of Midwifery Science, Amsterdam University Medical Centers Vrije Universiteit Amsterdam Amsterdam The Netherlands
3. Midwifery Academy Amsterdam Groningen, InHolland Amsterdam The Netherlands
4. Amsterdam Reproduction and Development Research Institute Amsterdam The Netherlands
5. Department of General Practice and Elderly Care Medicine University Medical Centre Groningen, University of Groningen Groningen The Netherlands
6. Division of Midwifery, School of Health Sciences University of Nottingham Nottingham UK
7. Department of Obstetrics and Gynecology Erasmus Medical Centre Rotterdam The Netherlands
8. Department of Obstetrics and Gynecology Amsterdam University Medical Centers, University of Amsterdam Amsterdam The Netherlands
9. Amsterdam Public Health Research Institute Amsterdam The Netherlands