Shigeki Matsubara1, Hironori Takahashi2, Yuji Takei2. 1. Department of Obstetrics and Gynecology, Jichi Medical University, 3311-1 Shimotsuke, Tochigi 329-0498, Japan. Electronic address: matsushi@jichi.ac.jp. 2. Department of Obstetrics and Gynecology, Jichi Medical University, 3311-1 Shimotsuke, Tochigi 329-0498, Japan.