[1] Sinai Hlth Syst, Lunenfeld Tanenbaum Res Inst, Dept Obstet & Gynaecol, Div Maternal Fetal Med, Toronto, ON, Canada
[2] Univ Toronto, Dept Obstet & Gynaecol, Toronto, ON, Canada
[3] Royal Free NHS Fdn Hosp, Dept Obstet & Gynaecol, London, England
[4] Royal Free NHS Fdn Hosp, Katharine Dormandy Haemophilia & Thrombosis Ctr, London, England
[5] UCL, Inst Womens Hlth, London, England
[6] Royal Free NHS Fdn Hosp, Dept Obstet & Gynaecol, Pond St, London NW3 2QG, England
[7] Royal Free NHS Fdn Hosp, Katharine Dormandy Haemophilia & Thrombosis Ctr, Pond St, London NW3 2QG, England