- Address correspondence and reprint requests to Qing Chen, MD, Department of Obstetrics and Gynecology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Yanjiang Road 107, Guangzhou, China, 510120. E-mail: .
- Received December 31, 2013
- Accepted April 1, 2014
- First published July 1, 2014.
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