1 Department of Public Health and Nursing, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Postboks 8905, 7491, Trondheim, Norway. eirin.haug@ntnu.no.
2 Department of Public Health and Nursing, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Postboks 8905, 7491, Trondheim, Norway.
3 Department of Obstetrics and Gynecology, Levanger Hospital, Nord-Trøndelag Hospital Trust, Levanger, Norway.
4 The Harvard T.H Chan School of Public Health, Harvard University, Boston, MA, USA.
5 Connors Center for Women's Health and Gender Biology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
6 MRC Integrative Epidemiology Unit and Population Health Sciences, University of Bristol, Bristol, UK.
7 Department of Endocrinology, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway.
The article was originally published electronically on the publisher's internet portal (currently SpringerLink) on 24 January 2018 without open access.