1. Department of Obstetrics and Gynecology; Kameda General Hospital; Kamogawa Chiba
2. Department of Environmental Health; National Institute of Public Health; Wako
3. Department of Obstetrics and Gynecology; School of Medicine; Kitasato University; Sagamihara
4. Department of Obstetrics and Gynecology; Hokkaido University Graduate School of Medicine; Sapporo Japan