1. Department of Epidemiology; Rollins School of Public Health; Emory University; Atlanta GA USA
2. Department of Obstetrics and Gynaecology; Kuopio University Hospital; Kuopio Finland
3. Department of Anaesthesia and Operative Services; Kuopio University Hospital; Kuopio Finland
4. School of Medicine; University of Eastern Finland; Kuopio Finland
5. National Institute for Health and Welfare (THL); Helsinki Finland
6. Nordic School of Public Health; Gothenburg Sweden