Funding for this research was provided by:
National Natural Science Foundation of China (81401755)
the Guangzhou Institute of Pediatrics/Guangzhou Women and Children's Medical Center (KCP-2016-002)
Received: 29 August 2019
Accepted: 11 November 2019
First Online: 16 December 2019
Ethics approval and consent to participate
: This work was approved by the commit of Guangzhou Women and Children’s Medical Center. The use of human subjects in this research has complied with all the relevant national regulations and institutional policies. All participants in the study gave their written informed consent. The research was approved by the author’s equivalent committee.
: All of authors have agreed to publication on BMC Pediatrics.
: No conflict of interest exits in the submission of this manuscript. All authors have read and approved this version of the article, and due care has been taken to ensure the integrity of the work.