Text and Data Mining valid from 2019-08-17
Received: 2 May 2019
Accepted: 6 August 2019
First Online: 17 August 2019
Ethics approval and consent to participate
: This study was approved by the Ethical Committee of the Women’s Hospital, School of Medicine, Zhejiang University.
: We obtained consent to publish this manuscript.
: The authors declare that they have no competing interests.