- Correspondence to Dr Shuiqing Ma, Obstetrics and Gynecology, Peking Union Medical College Hospital, Beijing 100730, China;
- Received April 15, 2019
- Revision received July 18, 2019
- Accepted August 21, 2019
- First published August 29, 2019.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.