1. School of Public Health, Oregon Health and Science University-Portland State University, Portland, Oregon, USA.
2. Department of Medicine, Solna, Clinical Epidemiology Division, Karolinska Institutet, Stockholm, Sweden.
3. Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, Oregon, USA.
4. Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden.
5. Department of Obstetrics and Gynecology, Karolinska University Hospital, Stockholm, Sweden.