1. Department of Obstetrics and Gynecology, MC Haaglanden, 2512 VA The Hague, The Netherlands
2. Department of Obstetrics, K6-P-35, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
3. Department of Obstetrics and Gynecology, Ikazia Hospital, 3008 AA Rotterdam, The Netherlands
4. Department of Obstetrics and Gynecology, Amsterdam Medical Center, 1105 AZ Amsterdam, The Netherlands