Received: 31 March 2021
Accepted: 2 June 2021
First Online: 14 June 2021
: This study was reviewed and approved by the institutional review board of Shanghai Institute of Planned Parenthood Research(reference number: 2012–01). All survey participants and their parents read and agreed to a written informed consent document prior to completing the survey and are given the right to skip any part of the survey or question. All methods were carried out in accordance with the ethical principles of the Declaration of Helsinki 1964.
: Not applicable.
: The authors declare that they have no competing interests.