1. Department of Pediatric Surgery, Kobe Children’s Hospital, Kobe 650-0047, Japan
2. Department of Pediatric Surgery, Shizuoka Children’s Hospital, Shizuoka 420-0953, Japan
3. Department of Public Health, Osaka Metropolitan University Graduate School of Medicine, Osaka 545-8585, Japan
4. Department of Pediatric Surgery, Kanagawa Children’s Medical Center, Yokohama 232-0066, Japan
5. Department of Neonatology, Kobe Children’s Hospital, Kobe 650-0047, Japan
6. Department of Obstetrics, Kobe Children’s Hospital, Kobe 650-0047, Japan