[1] Univ Birmingham, Dept Med, Haemostasis Thrombosis & Vasc Biol Unit, Ctr Cardiovasc Sci, Birmingham B18 7QH, W Midlands, England
[2] Russells Hall Hosp, Dept Surg, Dudley, England
[3] City Hosp, Dept Obstet & Gynaecol, Birmingham, W Midlands, England