1. Department of Community Dentistry Dental Faculty University of Oslo Oslo Norway
2. Department of Obstetrics and Gynecology Institute of Clinical Medicine, Akershus University Hospital Lørenskog Norway
3. Department of Dentistry – Quality and Safety of Oral Health Care Radboud Institute for Health Sciences, Radboud University Medical Center Nijmegen The Netherlands
4. Department of Community Dentistry, Dental Faculty University of Oslo Oslo Norway