Liu, Bo
Zhang, Jinglu
Yang, Dongxia
Article History
Received: 3 January 2019
Accepted: 12 June 2019
First Online: 22 June 2019
Ethics approval and consent to participate
: The study was approved by the ethics committee of Jinan Maternal & Children Health Care Hospital, and the written informed consent was obtained from all patients.
: Not applicable.
: The authors declare that they have no competing interests.