1. Department of Community Medicine, Faculty of Health Sciences, Linköping, Sweden, Correspondence address: Kristina Alexanderson, Department of Community Medicine, Faculty of Health Sciences, 581 85 Linköping, Sweden
2. Department of Obstetrics and Gynaecology, Faculty of Health Sciences, Linköping, Sweden
3. Department of Community Medicine, Faculty of Health Sciences, Linköping, Sweden
4. Tema Research Institute, Linköping University, Linköping, Sweden