1. Department of Obstetrics and Gynecology, Fukushima Medical University School of Medicine, Fukushima 960‑1295, Japan
2. Department of Diagnostic Pathology, Fukushima Medical University School of Medicine, Fukushima 960‑1295, Japan
3. Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai, Miyagi 980‑8574, Japan
4. Miyagi Cancer Center, Medeshima‑shiote, Natori, Miyagi 981‑1293, Japan
5. Department of Obstetrics and Gynecology, Faculty of Medicine, Yamagata University, Yamagata 990‑9585, Japan
6. Department of Obstetrics and Gynecology, Iwate Medical University School of Medicine, Morioka, Iwate 020‑8505, Japan
7. Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita 010‑8543, Japan
8. Department of Obstetrics and Gynecology, Hirosaki University School of Medicine, Hirosaki, Aomori 036‑8563, Japan