1. Department of Nursing, Okayama Prefectural University, Soja, Okayama, Japan.
2. Department of Obstetrics, Kaba Memorial Hospital, Hamamatsu, Shizuoka, Japan.
3. Department of Obstetrics, Seirei Hamamatsu General Hospital, Hamamatsu, Shizuoka, Japan.
4. Department of Human Ecology, Okayama University Graduate School of Environmental and Life Science, Okayama, Japan.
5. Department of Social Medicine, National Center for Child Health and Development, Tokyo, Japan.
6. Department of Epidemiology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan.
7. Department of Social and Behavioral Sciences, Harvard School of Public Health, Boston, MA, USA.