1. Department of Obstetrics and Gynecology; Keio University School of Medicine; Tokyo Japan
2. Department of Pediatrics; Keio University School of Medicine; Tokyo Japan
3. Department of Bone and Mineral Research; Research Institute; Osaka Women's and Children's Hospital; Osaka Japan
4. Department of Pediatric Imaging; Tokyo Metropolitan Children's Medical Center; Tokyo Japan
5. Division of Neonatology; Perinatal Center for Maternal and Child Health; Saitama City Hospital; Saitama Japan