1 Department of Obstetrics and Gynaecology, Amsterdam University Medical Center, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands; Amsterdam Reproduction and Development, Amsterdam, The Netherlands.
2 Department of Obstetrics and Gynaecology, Erasmus University Medical Center, University Medical Centre Rotterdam, Rotterdam, The Netherlands.
3 Department of Obstetrics & Gynaecology, Amsterdam University Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands. Electronic address: j.huirne@amsterdamumc.nl.