1Department of Obstetrics and Gynecology, Hirosaki University School of Medicine, Hirosaki, Japan
2Research Institute and Practice for Involutional Diseases, Nagano, Japan
3Department of Obstetrics and Gynecology, Narakenritsu Mimuro Hospital, Nara, Japan
4Department of Obstetrics and Gynecology, International University of Health and Welfare, Atami Hospital, Atami, Japan
5Department of Obstetrics and Gynecology, School of Medicine, Keio University, Tokyo, Japan
6Department of Obstetrics and Gynecology, Tone Central Hospital, Numata, Japan
7Department of Obstetrics and Gynecology, Dokkyo University School of Medicine, Tochigi, Japan
8Department of Obstetrics and Gynecology, Maebashi Kyouritu Hospital, Maebashi, Japan
9Department of Obstetrics and Gynecology, Kouseiren Yoshida General Hospital, Hiroshima, Japan
10Department of Obstetrics and Gynecology, Kagoshima University School of Medicine, Kagoshima, Japan
11Department of Obstetrics and Gynecology, Tokushima University School of Medicine, Tokushima, Japan
12Department of Obstetrics and Gynecology, Saitama Medical School, Saitama, Japan
13Department of Obstetrics and Gynecology, Niigata University School of Medicine, Niigata, Japan
14Department of Obstetrics and Gynecology, Ashikaga Red Cross Hospital, Tochigi, Japan
15Department of Basic Allied Medicine, School of Health Sciences, Faculty of Medicine, Gunma University, Maebashi, Japan