1 Department of Obstetrics and Gynecology, Jichi Medical University, 3311-1 Shimotsuke, Tochigi 329-0498, Japan.
2 Department of Obstetrics and Gynecology, Jichi Medical University, 3311-1 Shimotsuke, Tochigi 329-0498, Japan. Electronic address: hironori@jichi.ac.jp.