1. Department of Obstetrics and Gynecology, Oulu University Hospital, Wellbeing Services County of North Ostrobothnia, 90220 Oulu, Finland
2. Research Unit of Clinical Medicine, University of Oulu, 90220 Oulu, Finland
3. Medical Research Center, University of Oulu, Oulu University Hospital, Wellbeing Services County of North Ostrobothnia, 90220 Oulu, Finland
4. Department of Obstetrics and Gynecology, Helsinki University Hospital, University of Helsinki, 00290 Helsinki, Finland