[1] Univ Groningen, Univ Med Ctr Groningen, Dept Obstet & Gynecol, NL-9700 RB Groningen, Netherlands
[2] Onze Lieve Vrouw Hosp, Dept Obstet & Gynecol, Amsterdam, Netherlands
[3] Kennemer Gasthuis, Dept Obstet & Gynecol, Haarlem, Netherlands
[4] St Antonius Hosp, Dept Obstet & Gynecol, Nieuwegein, Netherlands
[5] Groene Hart Hosp, Dept Obstet & Gynecol, Gouda, Netherlands
[6] Bronovo Hosp, Dept Obstet & Gynecol, The Hague, Netherlands
[7] TweeSteden Hosp, Dept Obstet & Gynecol, Tilburg, Netherlands
[8] Martini Hosp, Dept Obstet & Gynecol, Groningen, Netherlands
[9] Bethesda Hosp, Dept Obstet & Gynecol, Hoogeveen, Netherlands
[10] CanisiusWilhelmina Hosp, Dept Obstet & Gynecol, Nijmegen, Netherlands
[11] Acad Med Ctr, Dept Obstet & Gynecol, Amsterdam, Netherlands
[12] Univ Groningen, Univ Med Ctr Groningen, Dept Epidemiol, Groningen, Netherlands