[1] Royal Hallamshire Hosp, Sheffield Haemophilia & Thrombosis Ctr, Sheffield, England
[2] Univ Crete, Sch Med, Lab Biostat, Iraklion, Heraklion, Greece
[3] Univ Sheffield, Sch Hlth & Related Res, Sheffield, England
[4] Royal Hallamshire Hosp, Dept Obstet & Gynaecol, Sheffield, England
[5] Univ Sheffield, Dept Cardiovasc Sci, Sheffield, England