Funding for this research was provided by:
the grant of Jiangsu province association of maternal and child health (FYX201603)
the Suzhou science and technology support program (SS201647)
the Suzhou Key Medical Center (Szzx201505)
Received: 6 March 2018
Accepted: 24 May 2018
First Online: 21 July 2018
Ethics approval and consent to participate
: The study was approved by the ethic committee. Informed consent was obtained.
: The authors declare that they have no competing interests.
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