1. Department of Obstetrics and Gynecology, Kurobe City Hospital, Mikkaichi 1108-1, Kurobe, Toyama, Japan
2. Department of Obstetrics and Gynecology, University of Toyama, Sugitani 2630, Toyama, Toyama, Japan
3. Department of Pathology, Kurobe City Hospital, Mikkaichi 1108-1, Kurobe, Toyama, Japan