[1] Univ Groningen, Univ Med Ctr Groningen, Dept Gen Practice & Elderly Care Med, Groningen, Netherlands
[2] Univ Maastricht, Maastricht Univ Med Ctr, Dept Gen Practice, Maastricht, Netherlands
[3] Maxima Med Ctr, Dept Obstet & Gynaecol, Veldhoven, Netherlands
[4] Univ Groningen, Univ Med Ctr Groningen, Dept Epidemiol, Groningen, Netherlands
[5] Univ Maastricht, Grow Res Sch Oncol & Dev Biol, Dept Obstet & Gynaecol, Maastricht, Netherlands