Funding for this research was provided by:
Key Discipline Construction Project of Pudong Health and Family Planning Commission of Shanghai (PWZxk2017-21)
Text and Data Mining valid from 2019-09-03
Received: 5 December 2017
Accepted: 28 August 2019
First Online: 3 September 2019
Ethics approval and consent to participate
: We verbally inform patients about the purpose of the study and the use of the data in a concise and understandable manner, and promise that all personal information collected will be kept confidential. The procedure has been approved by the ethics committee of Shanghai Pudong New Area Science and Technology Development (PKJ2012-18Y).
: Not applicable.
: The authors declare that they have no competing interests.