Xie, Yanxia
Mu, Yi http://orcid.org/0000-0002-6832-0954
Chen, Peiran http://orcid.org/0000-0001-7805-2095
Liu, Zheng
Wang, Yanping
Li, Qi
Li, Mingrong
Liang, Juan http://orcid.org/0000-0002-9354-1791
Zhu, Jun
Article History
Received: 23 October 2021
Accepted: 18 August 2022
First Online: 3 September 2022
Competing interests
: The authors declare no competing interests.
: The NMNMSS was established by the National Health Commission of the People’s Republic of China to improve the quality of maternal and child health in China. The NMNMSS was approved by the Ethics Committee of West China Second University Hospital, Sichuan University, China (Protocol ID: 2012008), and followed the tenets of the Declaration of Helsinki. Patient consent was collected by the surveillance hospitals of NMNMSS when the patient was admitted to the hospital. In addition to the establishment of the NMNMSS, ethical approval (Protocol ID: 2012008) also permitted use of patient data for further following studies (including this current study) on maternal health from the NMNMSS.