1. Medical School, National and Kapodistrian University of Athens; Assisted Reproduction Unit, 3rd Department of Obstetrics and Gynaecology; Attikon University Hospital Rimini 1 Athens Chaidari Greece 12462
2. Medical School, National and Kapodistrian University of Athens; 75 M. Assias Street Goudi Athens Greece 115 27
3. University of Athens; 3rd Department of Obstetrics and Gynecology; 'Attikon' Hospital, Chaidari Athens Greece
4. Attikon University Hospital; 2nd Department of Cardiology, University of Athens Medical School; Rimini 1 Haidari Athens Greece 12462
5. University of Oxford; Centre for Statistics in Medicine; Botnar Research Centre Windmill Road Oxford UK OX3 7LD