[1] St George Hosp, Maternal Med Serv, Dept Obstet, Blackshaw Rd, London SW17 0QT, England
[2] UCL EGA Inst Womens Hlth, London, England
[3] Hammersmith Hosp, Imperial Coll Healthcare NHS Trust, Dept Neurol, London, England
[4] Queen Charlottes & Chelsea Hosp, Imperial Coll Healthcare NHS Trust, Directorate Matern, London, England
[5] Royal London Hosp, Dept Obstet & Gynaecol, London, England
[6] Havering & Redbridge Univ Hosp NHS Trust, Queens Hosp Barking, Dept Obstet & Gynaecol, London, England
[7] Havering & Redbridge Univ Hosp NHS Trust, Queens Hosp Barking, Dept Neurol, London, England
[8] Chelsea & Westminster Hosp, Acad Dept Obstet & Gynaecol, London, England