1 Department of Obstetrics and Gynecology, Jichi Medical University, 3311-1 Shimotsuke, Tochigi 329-0498, Japan; Department of Obstetrics and Gynecology, Koga Red Cross Hospital, Ibaraki, Japan. Electronic address: matsushi@jichi.ac.jp.
2 Department of Pediatrics, Jichi Medical University, Shimotsuke, Japan.
3 Department of Surgery, Jichi Medical University, Shimotsuke, Japan.