[1] Univ Amsterdam, Acad Med Ctr, Dept Obstet & Gynaecol, Ctr Reprod Med, NL-1105 AZ Amsterdam, Netherlands
[2] Univ Amsterdam, Acad Med Ctr, Dept Vasc Med, NL-1105 AZ Amsterdam, Netherlands
[3] Univ Amsterdam, Acad Med Ctr, Dept Clin Epidemiol, NL-1105 AZ Amsterdam, Netherlands
[4] Liverpool Womens Hosp, Dept Obstet & Gynaecol, Liverpool, Merseyside, England
[5] Leiden Univ, Med Ctr, Dept Clin Epidemiol, Leiden, Netherlands
[6] Leiden Univ, Med Ctr, Dept Gen Internal Med, Leiden, Netherlands