[1] Zell Am See Hosp, Dept Obstet & Gynaecol, A-5700 Zell Am See, Austria
[2] Med Univ Vienna, Dept Obstet & Gynaecol, Div Gen Gynaecol & Gynaecol Oncol, A-1090 Vienna, Austria
[3] Med Univ Graz, Dept Obstet & Gynaecol, Div Gynaecol, A-8036 Graz, Austria
[4] Univ Hosp Freiburg, Dept Obstet & Gynaecol, Div Gynaecol, D-79106 Freiburg, Germany
[5] Med Univ Vienna, Ctr Med Stat Informat & Intelligent Syst, Sect Clin Biometr, A-1090 Vienna, Austria