[1] Belgian Canc Ctr, Sci Inst Publ Hlth, Canc Epidemiol Unit, B-1050 Brussels, Belgium
[2] Hannover Med Sch, Dept Obstet & Gynaecol, D-30625 Hannover, Germany
[3] Univ Toronto, Dalla Lana Sch Publ Hlth, Toronto, ON M5T 3M7, Canada
[4] Vrije Univ Amsterdam Med Ctr, Dept Pathol, NL-1081 HV Amsterdam, Netherlands