Funding for this research was provided by:
National key research and development program [grant numbers (2016YFC1000505, 2018YFC1002801)
Shanghai Municipal Commission of Health and Family Planning (201840184)
Innovation-oriented Science and Technology Grant from NHC Key Laboratory of Reproduction Regulation (CX2017-06)
Shandong Medical and Health Science and Technology Development Project (2018WS060)
Received: 18 May 2020
Accepted: 6 August 2020
First Online: 17 August 2020
Ethics approval and consent to participate
: The study was approved by the ethical review committee of Shanghai Institute of Planned Parenthood Research (SIPPR). Written informed consent was obtained before the data collection and analysis, and the survey was conducted in accordance with the Declaration of Helsinki Principles.
: Not applicable.
: The authors declare they have no actual or potential competing financial interests.