1. Reproductive Medicine Unit, University College London Hospital, London, UK
2. The Centre for Reproductive & Genetic Health, London, UK
3. Department of Haematology, University College London Hospital, London, UK
4. Department of Haematology, Whittington Health NHS Trust, London, UK
5. Gynaecology & Reproductive Medicine, Imperial College Healthcare NHS Trust, St Mary’s Hospital, London, W2 1NY and Department of Obstetrics & Gynaecology, Singapore General Hospital, Singapore, Singapore