Funding for this research was provided by:
National Natural Science Foundation of China (81501223)
The national key research and development program (2017YFC1001000)
Received: 29 March 2019
Accepted: 3 July 2019
First Online: 16 July 2019
Ethics approval and consent to participate
: Written informed contents were obtained from all participants. This study was approved by Institutional Review Board (IRB) of Reproductive Medicine, Shandong University.
: Not applicable.
: The authors declare that they have no competing interests.