[1] Oulu Univ Hosp, Dept Obstet & Gynecol, Oulu 90014, Finland
[2] St George Hosp, Sch Med, Diana Princess Wales Ctr Reprod Med, Acad Dept Obstet & Gynaecol, London, England
[3] Universitetsjukhuset MAS, Dept Obstet & Gynecol, Kvinnokliniken, Malmo, Sweden
[4] McGill Univ, Royal Victoria Hosp, Dept Obstet & Gynecol, Montreal, PQ H3A 1A1, Canada