Received: 20 July 2019
Accepted: 29 September 2020
First Online: 6 October 2020
Ethics approval and consent to participate
: A written approval letter was obtained from an institutional review board of Hangzhou First People’s Hospital (HFPH-IRB 2020KYYLS117-01). The authors declare that all samples involved in the study were collected with the written informed consents were obtained from the parents of infants. And there were no adolescent mothers (under the age of 18) in this study.
: Not applicable.
: The authors declare that they have no competing interests.