1. Wagatsuma T. Reproductive Health. Tokyo: Nankodo Co., Ltd., 2002. (in Japanese)
2. Ministry of Health and Welfare, Minister’s Secretariat. Statistics Information Bereau, Maternal body protection statistics reports. Tokyo: Health and Welfare Statistics Association, 2002. (in Japanese)
3. Health and Welfare Statistics Association. Vital Statistics. Tokyo: Health and Welfare Statistics Association, 2002 (in Japanese)
4. Centers for Disease Control and Prevention. Surveillance Summaries, November 29, 2002. MMWR. 2002; 51: 1–28.
5. Centers for Disease Control and Prevention. Surveillance Summaries. April 13, 2002. MMWR. 2002; 51: 1–32.