1. Department of Clinical Medicine; Section for Neurology; University of Bergen; Bergen Norway
2. Department of Neurology; Haukeland University Hospital; Bergen Norway
3. Department of Public Health and Primary Health Care; University of Bergen; Norway
4. Medical Birth Registry of Norway; Division of Epidemiology; Norwegian Institute of Public Health; Bergen Norway
5. The Norwegian Institute of Public Health; Oslo Norway
6. Nic Waals Institute; Lovisenberg Hospital; Oslo Norway