[1] Croydon Univ Hosp, Dept Obstet & Gynaecol, Thornton Heath, England
[2] Anglia Ruskin Univ, Sch Med, Chelmsford, Essex, England
[3] Basildon & Thurrock Univ Hosp, Womens Hlth Dept, Basildon, Essex, England
[4] Mayflower Healthcare Alliance, Billericay, Essex, England
[5] Croydon Univ Hosp, Dept Obstet & Gynaecol, 530 London Rd, Thornton Heath CR7 7YE, England