Received: 7 July 2021
Accepted: 21 March 2022
First Online: 8 April 2022
: The study’s protocols were reviewed and approved by the ethics committee of the Sun Yat-sen Memorial Hospital of Sun Yat-sen University (access number: ). Written informed consent form was obtained from subjects or member of the family. All methods were conducted in accordance with the ethical standards of the declaration of Helsinki. We only observed and evaluated their behavior as is routinely done in any NICU.
: Not applicable.
: The authors declare that they have no competing interests.