1. Department of Obstetrics and Gynecology, Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 550004, P.R. China
2. National and Guizhou Joint Engineering Laboratory for Cell Engineering and Biomedicine Technique, Center for Tissue Engineering and Stem Cell Research, Guizhou Province Key Laboratory of Regenerative Medicine, Guiyang, Guizhou 550004, P.R. China
3. Department of Obstetrics and Gynecology, Guizhou Provincial People's Hospital, Guiyang, Guizhou 550004, P.R. China