1. Department of Obstetrics and Gynecology, Faculty of Medical Sciences, University of Fukui, Fukui 910‑1193, Japan
2. Department of Obstetrics and Gynecology, Yokohama City University Graduate School of Medicine, Kanagawa 236‑0004, Japan
3. Department of Obstetrics and Gynecology, Osaka University Graduate School of Medicine, Osaka 565‑0871, Japan
4. Department of Obstetrics and Gynecology, Graduate School of Medicine, University of The Ryukyus, Okinawa 903‑0215, Japan