1. Department of Women's Health, University College London Hospitals, London NW1 2PG, UK
2. MRC Centre for Reproductive Health, University of Edinburgh, Edinburgh EH16 4TJ, UK
3. Department of Reproductive Medicine and Gynaecology, University Medical Centre Utrecht, Utrecht 3584 CX, The Netherlands
4. European Society of Human Reproduction and Embryology (ESHRE), Grimbergen B-1852, Belgium