1. Reproductive Medical Center, Department of Obstetrics and Gynecology, Southwest Hospital , Army Medical University , Chongqing , P.R. China
2. Department of Obstetrics and Gynecology , West China Second University Hospital, Sichuan University, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education , Chengdu , P.R. China
3. Reproductive Medical Center, Department of Obstetrics and Gynecology, Southwest Hospital , Army Medical University , 30 Gaotanyan Street, Shapingba District , Chongqing 400038 , P.R. China , Tel.: +86-23-13608356955, Fax: +86-23-68754410