Funding for this research was provided by:
National Institute of Child Health and Human Development (R01HD068165)
Received: 21 May 2018
Accepted: 20 December 2018
First Online: 3 January 2019
Ethics approval and consent to participate
: The study was reviewed and approved by the Institutional Review Boards of the University of California, Los Angeles in U.S. and the Anhui Provincial Center for Disease Control and Prevention in China. Written informed consent was obtained from all individual participants included in the study.
: Not Applicable.
: The authors declare that they have no competing interests.
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