1. Guizhou Prenatal Diagnosis Center, Affiliated Hospital of Guizhou Medical University, Guiyang 550004, Guizhou, P.R. China
2. School of Clinical Laboratory Science, Guizhou Medical University, Guiyang 550004, Guizhou, P.R. China
3. School of Basic Medical Sciences, Guizhou University of Traditional Chinese Medicine, Guiyang 550004, Guizhou, P.R. China
4. Reproductive Center, Affiliated Hospital of Guizhou Medical University, Guiyang 550004, Guizhou, P.R. China