Funding for this research was provided by:
Guangdong Medical Research Foundation (A2018255)
Received: 21 February 2020
Accepted: 15 June 2020
First Online: 19 June 2020
Compliance with Ethical Standards
: This study was approved by the Medical Research Ethics Board of the Guangdong Women and Children’s Hospital, and informed consent was obtained from the parents of each child.
: The authors declare that they have no conflict of interest.