1. School of Medicine, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
2. Division of Neonatology, Department of Pediatrics, Chang Gung Memorial Hospital, Kaohsiung 833, Taiwan
3. Division of Neonatology, Department of Pediatrics, Linkou Chang Gung Memorial Hospital, Taoyuan 333, Taiwan
4. Division of Pediatric Gastrointestinal Disease, Department of Pediatrics, Chang Gung Memorial Hospital, Chiayi 613, Taiwan
5. Division of Neonatology and Pediatric Hematology/Oncology, Department of Pediatrics, Chang Gung Memorial Hospital, Yunlin 638, Taiwan