1. Department of Prenatal Diagnosis Center, General Hospital of Ningxia Medical University, Yinchuan, Ningxia 750004, P.R. China
2. Department of Public Health, Xi'an Jiaotong University College of Medicine, Xi'an, Shaanxi 710061, P.R. China
3. Key Laboratory of Cardiovascular and Cerebrovascular Diseases, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R. China
4. Department of Pathophysiology, Basic Medical School, Ningxia Medical University, Yinchuan, Ningxia 750004, P.R. China