Lian, Qiguo
Zuo, Xiayun
Zhong, Xiangyang
Tu, Xiaowen
Zhang, Jiashuai
Shu, Chang
Yu, Chunyan
Lou, Chaohua
Article History
Received: 7 December 2020
Accepted: 2 August 2021
First Online: 10 August 2021
Declarations
:
: During the ongoing Covid-19 pandemic, we obtained negative consent from the parents or guardians and active consent from subjects remotely using digital method.The study was reviewed and approved by the institutional ethics board of Shanghai Institute of Planned Parenthood Research, and follows the ethical principles of the Declaration of Helsinki 1964.
: None declared.
: Not applicable.