Liu, Weiling
Lu, Yaping
Fan, Yuqin
Hei, Guozhen
Zhang, Aijuan
Xue, Guoping
Wu, Yanmei
Article History
Received: 23 November 2022
Accepted: 5 September 2023
First Online: 7 September 2023
Declarations
:
: The authors declare no competing interests.
: The study was conducted following the Declaration of Helsinki guidelines. The study protocol was reviewed and approved by the ethics committee of Shandong Provincial Maternal and Child Health Care Hospital Affiliated to Qingdao University. The ethics committee of Shandong Provincial Maternal and Child Health Care Hospital Affiliated to Qingdao University agreed to waive the written informed consent due to the retrospective nature of the study.
: Not applicable.