1. Department of Obstetrics and Gynecology, Iwate Prefectural Iwai Hospital, Kozenji, Ichinoseki-city, 029-0192, Japan
2. Department of Obstetrics and Gynecology, Tohoku University Hospital, 1-1, Seiryo-machi, Aoba-ku, Sendai-city, Miyagi 980-8574, Japan