Funding for this research was provided by:
the National Natural Science Foundation of China (81741027, 81300533, 81601276)
Reproductive Medicine Young Physicians Research and Development project (17020160685, 16020220638)
Text and Data Mining valid from 2019-01-03
Received: 15 October 2018
Accepted: 12 December 2018
First Online: 3 January 2019
Ethics approval and consent to participate
: The study was approved by the Research Ethics Committee of Yantai Yuhuangding Hospital.
: Not applicable.
: The authors declare that they have no competing interests.
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