Funding for this research was provided by:
science and technology bureau project of Xuzhou (NO 18182)
Received: 6 August 2019
Accepted: 20 January 2020
First Online: 6 February 2020
Ethics approval and consent to participate
: This study was approved by Xuzhou Central Hospital Ethics Committee. The approval number is XZXY-LJ-20161121-021.
: All authors consent for publication. The pregnant woman signed the consent form of BioMed central.
: The authors declare that they have no competing interests.