1. Fetal Medicine Unit, St George's University Hospitals NHS Foundation Trust University of London London UK
2. Vascular Biology Research Centre, Molecular and Clinical Sciences Research Institute St George's University of London London UK
3. Department of Women's and Children's Health Karolinska Institute Stockholm Sweden
4. Astrid Lindgren Children's Hospital Karolinska University Hospital Stockholm Sweden
5. The Royal College of Obstetricians and Gynaecologists London UK
6. University College London Hospitals NHS Foundation Trust London UK
7. Norfolk and Norwich University Hospitals NHS Foundation Trust Norwich, Norfolk UK
8. North Bristol NHS Trust Department of Women's Health Westbury on Trym UK
9. Imperial College London London UK
10. Paediatric Infectious Diseases Research Group and Vaccine Institute, Institute of Infection and Immunity St George's University of London London UK
11. Immunisation and Countermeasures Division, Public Health England
12. British Paediatric Surveillance Unit, Royal College of Paediatrics and Child Health London UK