1. Preventive Medicine Center, International University of Health and Welfare, Mita Hospital, Tokyo, Japan.
2. Department of Obstetrics, Tokyo Health Service Association, Tokyo, Japan.
3. Saku Central Hospital Advanced Care Center, Nagano Prefectural Federation of Agricultural Cooperatives for Health and Welfare, Nagano, Japan.
4. Division of International Collaborative Research, Center for Public Health Sciences, National Cancer Center, Tokyo, Japan.
5. Koukan Clinic, Nippon Koukan Hospital, Kanagawa, Japan.
6. Department of Obstetrics and Gynecology, Faculty of Medicine, Kyorin University, Tokyo, Japan.
7. Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo, Japan.