Funding for this research was provided by:
Health and Family Planning Commission of Hubei Province (WJ2018H0133)
key projects of Natural Science Foundation in Hubei Province (2019CFA033)
Received: 11 August 2019
Accepted: 28 September 2020
First Online: 12 October 2020
Ethics approval and consent to participate
: The study conformed to the guidelines explained in the Declaration of Helsinki and was approved by the ethics committee of Maternal and Child Health Hospital of Hubei Province (MCHHHP, Wuhan, China). A waiver for the requirement of informed consent from the patients whose records were analyzed was granted by the Chair of the Committee on the grounds of being a minimal risk study.
: Not applicable.
: The authors declare that they have no competing interests.