[1] Chelsea & Westminster Hosp, Acad Dept Obstet & Gynaecol, London SW10 9NH, England
[2] Univ Hosp Bristol NHS Fdn Trust, Adult Congenital Heart Dis Serv, Bristol, Avon, England
[3] Univ Hosp Bristol NHS Fdn Trust, Dept Obstet, Bristol, Avon, England
[4] Oxford Univ Hosp NHS Fdn Trust, Womens Ctr, Oxford, England
[5] Oxford Univ Hosp NHS Fdn Trust, NIHR Oxford Biomed Res Ctr, Oxford, England
[6] Leeds Teaching Hosp NHS Trust, Dept Adult Congenital Heart Dis, Leeds, W Yorkshire, England
[7] Univ Southampton, Princess Anne Hosp, Dept Human Dev & Hlth, Southampton, Hants, England
[8] Glenfield Hosp, Dept Adult Congenital Heart Dis, Leicester, Leics, England
[9] Royal Leicester Infirm, Dept Obstet, Leicester, Leics, England
[10] Golden Jubilee Natl Hosp, Scottish Adult Congenital Cardiac Serv, Glasgow, Lanark, Scotland
[11] Univ Coll Hosp, Dept Obstet, London, England
[12] Barts Heart Ctr, Dept Adult Congenital Heart Dis, London, England