Received: 9 September 2020
Accepted: 22 December 2020
First Online: 8 January 2021
Ethics approval and consent to participate
: The ethics committee of the Institutional Review Board of the Seoul National University Hospital approved this retrospective study (IRB number: 1910–051-1068, approved date: Oct 14th, 2019) and we could access the medical records data with this approval. Given the retrospective and grave nature of our study, the need for retrospective parental consent was waived by the Institutional Review Board of the Seoul National University Hospital.
: Not applicable.
: The authors declare that they have no competing interests.