- Correspondence to Dr Xiaoye Wang, Gynaecology and Obstetrics Department, Peking University Third Hospital, Beijing, 100191, China; and Professor Hong Zhou, Department of Maternal and Child Health, School of Public Health, Peking University, Beijing, 100191, China;
- Received June 12, 2017
- Revised May 31, 2018
- Accepted June 19, 2018
- First published August 6, 2018.
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