1 Nuffield Department of Women's & Reproductive Health, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom; Fetal Medicine Unit, Department of Maternal and Fetal Medicine, Women's Center, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom.
2 Fetal Medicine Unit, Department of Maternal and Fetal Medicine, Women's Center, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom.
3 Nuffield Department of Women's & Reproductive Health, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom. Electronic address: aris.papageorghiou@wrh.ox.ac.uk.