Received: 23 April 2020
Accepted: 8 July 2020
First Online: 16 July 2020
Ethics approval and consent to participate
: This study was approved by the Juntendo University Ethics Committee and conducted in accordance with the principles of the Declaration of Helsinki. All were admitted to the neonatal intensive care unit (NICU) of Juntendo University Shizuoka Hospital between July 2017 and August 2019, and their parents had provided written informed consent for inclusion in the study.
: Not applicable
: The authors declare that they have no competing interests.