1 Department of Obstetrics and Gynecology, Jichi Medical University, Tochigi, Japan; Department of Obstetrics and Gynecology, Koga Red Cross Hospital, 1150 Shimoyama, Koga, Ibaraki 306-0014, Japan. Electronic address: matsushi@jichi.ac.jp.
2 Department of Surgery, Jichi Medical University, Japan. Electronic address: alefor@jichi.ac.jp.