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)
Text and Data Mining valid from 2018-07-21
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.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.