[1] Karolinska Univ Hosp, Karolinska Inst, Dept Woman & Child Hlth, Div Obstet & Gynaecol, S-17176 Stockholm, Sweden
[2] Akershus Univ Hosp, Dept Obstet & Gynaecol, Oslo, Norway
[3] Univ Edinburgh, Royal Infirm Edinburgh, Dept Pathol, Edinburgh, Midlothian, Scotland