[1] Karolinska Univ Hosp, Dept Obstet & Gynaecol, Sect Obstet, Stockholm 17176, Sweden
[2] Univ London St Georges Hosp, Div Clin Dev Sci, Sect Obstet & Gynaecol, London, England
[3] Sahlgrenska Acad KK, East Hosp, Perinatal Ctr, Gothenburg, Sweden
[4] Univ Hosp, Dept Obstet & Gynaecol, Lund, Sweden
[5] Univ Utrecht, Med Ctr, Dept Obstet & Gynaecol, Utrecht, Netherlands