Funding for this research was provided by:
National Natural Science Foundation of China (81903039)
The Sixth people's hospital of Shanghai medical group projects (ly201802)
Sponsored by Shanghai Sailing Program (19YF1444500)
Changning district committee of science and technology (CNKW2017Y07)
Project supported by Shanghai Tongren Hospital (TRYJ201605)
Changning district health and family planning commission (20164Y003)
Text and Data Mining valid from 2020-03-24
Received: 1 November 2019
Accepted: 28 February 2020
First Online: 24 March 2020
Ethics approval and consent to participate
: If the participant is a child (under 16) from a parent or guardian, the informed consent to participate has been obtained.This retrospective study was approved and consented to participate by the Ethics Committee. The written informed consent of the subject has been obtained.
: Not applicable.
: The authors declare that they have no competing interests.