1. Clinical Epidemiology Unit Qilu Hospital of Shandong University Jinan Shandong China
2. Clinical Research Center of Shandong University, Qilu Hospital Cheeloo College of Medicine, Shandong University Jinan Shandong China
3. Department of Epidemiology and Health Statistics, School of Public Health Cheeloo College of Medicine, Shandong University Jinan Shandong China
4. Department of Obstetrics and Gynecology Qilu Hospital of Shandong University Jinan Shandong China