[1] Univ Amsterdam, Amsterdam Reprod & Dev Res Inst, Dept Obstet & Gynecol, Amsterdam UMC, Amsterdam, Netherlands
[2] Univ Amsterdam, Amsterdam Univ Med Ctr, Dept Clin Epidemiol Biostat & Bioinformat, Amsterdam, Netherlands
[3] Pregnancy Sickness Support, Bodmin, Cornwall, England
[4] Noordwest Ziekenhuisgrp, Dept Obstet & Gynecol, Alkmaar, Netherlands
[5] Univ Amsterdam, Amsterdam Univ Med Ctr, Lab Reprod Biol, Amsterdam, Netherlands
[6] Reinier de Graaf Hosp, Dept Obstet & Gynecol, Delft, Netherlands
[7] Martini Hosp, Dept Obstet & Gynecol, Groningen, Netherlands
[8] Radboud Univ Nijmegen, Dept Obstet & Gynecol, Med Ctr, Nijmegen, Netherlands
[9] Gelre Hosp, Dept Obstet & Gynecol, Apeldoorn, Netherlands
[10] Flevo Hosp, Dept Obstet & Gynecol, Almere, Netherlands
[11] Catharina Hosp, Dept Obstet & Gynecol, Eindhoven, Netherlands
[12] Maxima Med Ctr, Dept Obstet & Gynecol, Veldhoven, Netherlands
[13] Zuyderland Hosp, Dept Obstet & Gynecol, Heerlen, Netherlands
[14] Franciscus Gasthuis, Dept Obstet & Gynecol, Rotterdam, Netherlands
[15] Amphia Hosp, Dept Obstet & Gynecol, Breda, Netherlands
[16] Scheper Hosp, Dept Obstet & Gynecol, Emmen, Netherlands
[17] Spaarne Gasthuis, Dept Obstet & Gynecol, Haarlem, Netherlands
[18] OLVG, Dept Obstet & Gynecol, Amsterdam, Netherlands
[19] Jeroen Bosch Hosp, Dept Obstet & Gynecol, sHertogenbosch, Netherlands
[20] Maastricht Univ, Dept Obstet & Gynecol, Med Ctr, Maastricht, Netherlands
[21] Diakonessen Hosp, Dept Obstet & Gynecol, Utrecht, Netherlands
[22] Monash Univ, Dept Obstet & Gynecol, Clayton, Vic, Australia