Funding for this research was provided by:
Key Developing Discipline of Shanghai Municipal Commission of Health and Family Planning (2016ZB0101)
Received: 30 December 2019
Revised: 16 May 2020
Accepted: 27 May 2020
First Online: 11 June 2020
Compliance with ethical standards
: The study protocol was approved by the ethical committees/institutional review boards as required at each participating center. Written parental consent, as well as assent from patients when appropriate was obtained.
: The authors declare that they have no conflict of interest.