Funding for this research was provided by:
Beijing Municipal and Commission Health and Family Planning (2015-3-076)
Received: 26 October 2019
Accepted: 7 January 2020
First Online: 16 January 2020
Ethics approval and consent to participate
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the Ethics Committee of Beijing Children’s Hospital (No. 2017–23) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Participant consent was written by the guardian of all the patients and informed consent forms were archived.
: Not applicable.
: The authors declare that they have no competing interests.