[1] Univ Amsterdam, Acad Med Ctr, Dept Obstet & Gynecol, NL-1105 AZ Amsterdam, Netherlands
[2] Univ Amsterdam, Acad Med Ctr, Dept Clin Epidemiol & Biostat, NL-1105 AZ Amsterdam, Netherlands
[3] Birmingham Womens Hlth Care NHS Trust, Dept Obstet & Gynecol, Birmingham, W Midlands, England
[4] Univ Zurich, Horten Ctr, Zurich, Switzerland
[5] Univ Lund Hosp, Dept Obstet & Gynecol, S-22185 Lund, Sweden
[6] Sandwell & W Birmingham Hosp NHS Trust, Dept Obstet & Gynecol, Birmingham, W Midlands, England
[7] Univ Hosp Leuven, Dept Obstet & Gynecol, Leuven, Belgium
[8] Erasmus MC, Dept Obstet & Gynecol, Rotterdam, Netherlands
[9] Univ Edinburgh, Dept Reprod & Dev Sci, Edinburgh, Midlothian, Scotland
[10] Univ Fed Sao Paulo, Dept Gynecol, Escola Paulista Med, Sao Paulo, Brazil
[11] Univ Sassari, Dept Gynecol, I-07100 Sassari, Italy
[12] Rijnstate Hosp, Dept Obstet & Gynecol, Arnhem, Netherlands
[13] Univ Amsterdam, Acad Med Ctr, Dept Gen Practice, NL-1105 AZ Amsterdam, Netherlands