1. Department of Obstetrics and Gynecology; Turku University Central Hospital; Turku; Finland
2. Department of Obstetrics and Gynecology; University of Turku; Turku; Finland
3. Department of Biostatistics; University of Turku; Turku; Finland
4. Department of Obstetrics and Gynecology; Oulu University Hospital; Oulu; Finland
5. Department of Obstetrics and Gynecology; Kätilöopisto Maternity Hospital; Helsinki; Finland
6. Department of Obstetrics and Gynecology; Tampere University Hospital; Tampere; Finland