1. 1Department of Obstetrics and Gynaecology, The Royal London Hospital, Barts Health NHS Trust, London, UK
2. 2Women’s Health Research Unit, Queen Mary University of London, London, UK
3. 3Department of Gynecology, Norfolk & Norwich University Hospital, Norwich, UK
4. 4Poole Hospital NHS Foundation Trust, UK
5. 5Barts and the London Pragmatic Clinical Trials Unit, Queen Mary University of London, London, UK
6. 6Women’s Health Research Unit, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
7. 7MRC Centre for Reproductive Health, University of Edinburgh, UK
8. 8Institute of Metabolism and Systems Research and Institute of Applied Health Research, University of Birmingham, Birmingham, UK
9. 9UCL Social Research Institute, University College London, London, UK