[1] Soder Sjukhuset, Dept Clin Sci & Educ, Karolinska Inst, Div Obstet & Gynaecol, S-11883 Stockholm, Sweden
[2] Danderyd Hosp, Karolinska Inst, Dept Clin Sci, Div Obstet & Gynecol, Stockholm, Sweden
[3] Karolinska Univ Hosp Huddinge, Karolinska Inst, CLINTEC, Unit Obstet & Gynecol, Stockholm, Sweden
[4] Roskilde Univ Hosp, Dept Obstet & Gynecol, Roskilde, Denmark
[5] Karolinska Inst, Dept Med Epidemiol & Biostat, Stockholm, Sweden