1. Department of Obstetrics and Gynecology, Research Unit of Clinical Medicine, Medical Research Center Oulu, University of Oulu, Oulu University Hospital, Oulu, Finland
2. Department of Obstetrics and Gynecology, University of Helsinki, Helsinki University Hospital, Helsinki, Finland
3. Department of Obstetrics and Gynecology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden