Article History
Received: 6 March 2021
Accepted: 21 July 2021
First Online: 30 July 2021
Declarations
:
: The authors declare that they have no competing interests, including: the authors have no relevant financial or non-financial interests to disclose. The authors have no conflicts of interest to declare that are relevant to the content of this article. All the authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript. The authors have no financial or proprietary interests in any material discussed in this article.
: This study was approved by the ethics committee of Dongguan Maternal and Child Health Hospital on September 30, 2018 (No. [23] 2018).
: All the participants signed informed consent before the examination.