Received: 10 January 2021
Accepted: 17 May 2021
First Online: 25 June 2021
: This study was performed in accordance with the Declaration of Helsinki and has been approved by the Ethics Committee of the Affiliated Hospital of Xuzhou Medical University (XYFY2020-KL135-01), Informed consent was obtained over the phone and verbal consent from all mothers for their data to be used for research and the procedure was approved by the Ethics Committee of the Affiliated Hospital of Xuzhou Medical University.
: Not applicable.
: The authors declare that they have no competing interests.