1. Department of Obstetrics and Gynecology, Academic Medical Center, P.O. Box 22770, 1100 DE Amsterdam, The Netherlands
2. Department of Obstetrics and Gynaecology, Flevo Hospital, P.O. Box 3005, 1300 EG Almere, The Netherlands
3. Department of Obstetrics and Gynaecology, VUmc, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands
4. The Robinson Institute, School of Paediatrics and Reproductive Health, University of Adelaide, 55 King William Road, North Adelaide, Adelaide, SA 5006, Australia