Shigeki Matsubara1,2. 1. Department of Obstetrics and Gynecology, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan. matsushi@jichi.ac.jp. 2. Department of Obstetrics and Gynecology, Koga Red Cross Hospital, 1150 Shimoyama, Koga, Ibaraki, 306-0014, Japan. matsushi@jichi.ac.jp.