1. National Institute for Health and Welfare, Oulu, Finland
2. Department of Obstetrics and Gynecology, Kuopio University Hospital, Kuopio, Finland
3. Department of Dermatology, Medical University, Vienna, Austria
4. Department of Obstetrics and Gynecology, University of Helsinki, Helsinki, Finland
5. School of Public Health, University of Tampere, Tampere, Finland