L B Romundstad1, S Opdahl2, A Pinborg3. 1. Department of Public Health, Norwegian University of Science and Technology (NTNU), Trondheim, Norway Spiren Fertilitetsklinikk, IVF Unit, Trondheim, Norway liv.b.romundstad@ntnu.no. 2. Department of Public Health, Norwegian University of Science and Technology (NTNU), Trondheim, Norway. 3. Department of Obstetrics and Gynecology, Hvidovre Hospital, Institute of Clinical Medicine, Copenhagen University Hospital, Copenhagen, Denmark.