1. Department of Obstetrics and Gynecology, Heilongjiang University of Chinese Medicine, Harbin 150040, China
2. Department of Obstetrics and Gynecology, The First Affiliated Hospital of Heilongjiang University of Chinese Medicine, Harbin 150040, China
3. Center for Post-Doctoral Studies, Heilongjiang University of Chinese Medicine, Harbin 150040, China
4. Pennsylvania State University College of Medicine, Hershey, PA 17033, USA