1. Division of Public Health and Epidemiology, Department of Social Medicine, Asahikawa Medical University, Asahikawa, Japan
2. Department of Obstetrics and Gynecology, Asahikawa Medical University, Asahikawa, Japan
3. Department of Pediatrics, Asahikawa Medical University, Asahikawa, Japan
4. Faculty of Nursing, Japanese Red Cross Hokkaido College of Nursing, Hokkaido, Japan
5. Center for Environmental and Health Sciences, Hokkaido University, Sapporo, Japan
6. Faculty of Health Sciences, Hokkaido University, Sapporo, Japan