1 Fetal Medicine Unit, St George's Hospital, St George's University of London, London, United Kingdom; Department of Statistics, Faculty of Arts and Science, Middle East Technical University, Çankaya/Ankara, Turkey.
2 Fetal Medicine Unit, St George's Hospital, St George's University of London, London, United Kingdom.
3 Fetal Medicine Unit, St George's Hospital, St George's University of London; Vascular Biology Research Centre, Molecular and Clinical Sciences Research Institute, St George's University of London, London, United Kingdom.
4 Fetal Medicine Unit, St George's Hospital, St George's University of London; Vascular Biology Research Centre, Molecular and Clinical Sciences Research Institute, St George's University of London, London, United Kingdom. Electronic address: akhalil@sgul.ac.uk.