1. Department of Obstetrics and Gynecology, Copenhagen University Hospital Hvidovre, Kettegård Allé 26, Hvidovre, Denmark
2. Fertility Clinic, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, KBH Ø, Denmark
3. University of Copenhagen, Department of Public Health, Section of Biostatistics, Øster Farimagsgade 5, DK-1014 KBH K, Denmark