1. Obstetrics Department, Aragon Institute of Health Research, IIS Aragón, Hospital Clínico Universitario Lozano Blesa, Zaragoza, Spain;
2. Nuffield Department of Women’s and Reproductive Health, University of Oxford, John Radcliffe Hospital, Oxford, UK;
3. Department of Maternal and Fetal Medicine, Fetal Medicine Unit, Women’s Center, John Radcliffe Hospital, Oxford University Hospitals National Health Service Foundation Trust, Oxford, UK