Funding for this research was provided by:
National Natural Science Foundation of China (30872164 & 81172758)
Guangdong Science & Technology Plan (2016A020218014)
Text and Data Mining valid from 2018-03-22
Received: 11 September 2017
Accepted: 14 March 2018
First Online: 22 March 2018
Ethics approval and consent to participate
: The Institutional Review Board of the public health school of the Sun Yat-Sen University approved the study, and every single pregnant woman was recruited with informed consent.
: The authors declare that they have no competing interests.
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