1. Department of Gynecology, National Cancer Center Hospital, Tokyo, JAPAN
2. JCOG Data Center/Operations Office, National Cancer Center Hospital, Tokyo, JAPAN
3. Division of Obstetrics and Gynecology, Tohoku Medical and Pharmaceutical University, Miyagi, JAPAN
4. Department of Obstetrics & Gynecology, Faculty of Medicine, Kagoshima University, Kagoshima, JAPAN
5. Department of Obstetrics and Gynecology, Tohoku University School of Medicine, Miyagi, JAPAN