1. Department of Obstetrics and Gynecology, Hospital Nova of Central Finland, Jyväskylä, Finland
2. Department of Obstetrics and Gynecology, University of Turku, Turku, Finland
3. Department of Public Health, University of Turku, Turku, Finland
4. Department of Biostatistics, University of Turku, Turku, Finland
5. Turku Clinical Research Centre, Turku University Hospital, Turku, Finland
6. Department of Obstetrics and Gynecology, Turku University Hospital, Turku, Finland