1. Twins Research AustraliaThe University of Melbourne Melbourne Australia
2. Fetal Medicine Unit, St George's University Hospitals NHS Foundation TrustUniversity of London London UK
3. Twins and Multiple Births Association London UK
4. Institute for Women's HealthUniversity College London London UK
5. Nuffield Department of Primary Care Health SciencesUniversity of Oxford Oxford UK
6. Vascular Biology Research Centre, Molecular and Clinical Sciences Research InstituteSt George's University of London London UK
7. London, UK
8. Johns Hopkins Center for Fetal Therapy, Department of Gynecology & Obstetrics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
9. BCNatal, Barcelona Centre de Medicina Maternofetal i Neonatal Hospital Clínic i Hospital Sant Joan de Déu, Universitat de Barcelona, Sabino de Arana, Barcelona, Spain
10. Fetal Medicine Unit, St George's University of London, London, UK
11. Murdoch Children's Research Institute, Melbourne, Australia
12. Twins Research Australia, Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
13. Elizabeth Bryan Multiple Births Centre, Birmingham City University, Birmingham, UK
14. Institute for Women's Health, University College London, London; and Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK
15. Leiden, The Netherlands
16. Twins and Multiple Births Association, London, UK
17. Australian Multiple Birth Association, Melbourne, Australia; International Council of Multiple Birth Organisations
18. Multiples of America, USA
19. Norwegian Institute of Public Health, Oslo, Norway
20. Twinning It UK, London, UK
21. University Medical Center Hamburg‐Eppendorf, Hamburg, Germany
22. Nord University, Finland
23. Departments of Obstetrics, Gynecology and Reproductive Sciences and Pediatric Surgery, The University of Texas Health Science Center, The Fetal Center, Children's Memorial Hermann Hospital, Houston, TX, USA
24. University of Birmingham, London, UK
25. Twins Research Australia, The University of Melbourne, Melbourne, Australia
26. University Hospitals Leuven, Antwerp Area, Belgium
27. Multiples New Zealand, New Zealand; International Council of Multiple Birth Organisations
28. Leids Universitair Medisch Centrum, Leiden, The Netherlands
29. International Council of Multiple Birth Organisations
30. Neonatal Unit, St George's University of London, London, UK
31. Medical University of Vienna, Vienna, Austria
32. Australian Multiple Birth Association, Melbourne, Australia
33. Department of Maternal‐Fetal Medicine, The Royal Women's Hospital, Obstetrics and Gynaecology, The University of Melbourne, Melbourne, Australia
34. University of Rome Tor Vergata, Rome, Italy
35. Departments of Child Health, Obstetrics and Gynaecology and Radiology, Clinical and Experimental Sciences, University of Southampton, Southampton, UK
36. Lewisham and Greenwich NHS Hospital, Lewisham, UK
37. Swinburne University of Technology, Melbourne, Australia
38. Amsterdam University Medical Centre, Amsterdam, The Netherlands