1 Department of Obstetrics and Gynecology, Jichi Medical University, Tochigi, Japan; Department of Obstetrics and Gynecology, Koga Red Cross Hospital, 1150 Shimoyama, Koga, Ibaraki 306-0014, Japan; Medical Examination Center, Ibaraki Western Medical Center, 555 Otsuka, Chikusei, Ibaraki 308-0813, Japan. Electronic address: matsushi@jichi.ac.jp.
2 Department of Pediatrics, Jichi Medical University, Tochigi, Japan. Electronic address: 99081dm@jichi.ac.jp.