1 Fetal Medicine Unit, Department of Obstetrics and Gynaecology, St George's Hospital, St George's University of London, London SW17 0QT, UK; Vascular Biology Research Centre, Molecular and Clinical Sciences Research Institute, St George's University of London, London SW17 0QT, UK. Electronic address: akhalil@sgul.ac.uk.
2 Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden; Department of Neonatology, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden.
3 The Royal College of Obstetricians and Gynaecologists, London, UK; Department of Women's Health, University College London Hospitals NHS Foundation Trust, London, UK.
4 Department of Gynecology and Obstetrics, Hospital das Clínicas, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil.
5 Department of Gynecology and Obstetrics, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil.
6 Paediatric Infectious Diseases Research Group and Vaccine Institute, Institute of Infection and Immunity, St George's University of London, London SW17 0QT, UK; Immunisation and Countermeasures Division, Public Health England, London, UK; British Paediatric Surveillance Unit, Royal College of Paediatrics and Child Health, London, UK.