1. Department of Obstetrics and Gynaecology, Onze Lieve Vrouwe Gasthuis, Amsterdam, the Netherlands
2. Department of Obstetrics and Gynaecology, University Medical Centre Utrecht, Utrecht, the Netherlands
3. Department of Epidemiology, Onze Lieve Vrouwe Gasthuis, Amsterdam, the Netherlands
4. Department of Quality and Safety, St. Antoniusziekenhuis, Nieuwegein, the Netherlands
5. Department of Behavioral Sciences, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, the Netherlands