1. Medical Care Planning Division, Health Policy Bureau, Ministry of Health, Labour and Welfare; Chiyoda-ku; Tokyo Japan
2. Department of Obstetrics and Gynecology, Faculty of Medicine, The University of Tokyo; Bunkyo-ku; Tokyo Japan
3. Department of Obstetrics and Gynecology, Tama-Nagayama Hospital; Nippon Medical School; Tokyo Japan
4. Division of the Health for the Elderly, Ministry of Health, Labour and Welfare; Chiyoda-ku; Tokyo Japan
5. Department of Neonatology, Maternal And Perinatal Center of Tokyo Women's Medical University; Shinjuku; Tokyo Japan
6. Department of Obstetrics and Gynecology, Kitasato University School of Medicine; Minami-ku; Sagamihara city Japan
7. Division of Neonatal Medicine, Center for Maternal, Fetal and Neonatal Medicine, Saitama Medical Center; Saitama Medical University; Kawagoe Saitama Japan