[1] Univ Hosp Birmingham, Birmingham B15 2TH, W Midlands, England
[2] St Thomas Hosp, London, England
[3] St Bartholomews Hosp, Barts Sexual Hlth Ctr, London, England
[4] Univ London Imperial Coll Sci Technol & Med, Hammersmith Hosp, Dept Cardiovasc Med, London, England
[5] Middlesex Hosp, London, England
[6] Elizabeth Garrett Anderson Obstet Hosp, London, England
[7] Univ London Imperial Coll Sci Technol & Med, Queen Charlottes & Chelsea Hosp, Inst Reprod & Dev Biol, London, England
[8] UCL, London WC1E 6BT, England
[9] Margaret Pyke Mem Trust, London, England