1. Lanzhou University; The First Clinical College of Lanzhou University; Evidence-Based Medicine Center, School of Basic Medical Sciences; No. 199, Donggang West Road Lanzhou City Gansu China 730000
2. Hospital of Lanzhou City; Maternity and Child-care; West Shizi Lanzhou City Ganshu China 730000
3. Lanzhou University; Evidence-Based Medicine Center, School of Basic Medical Sciences; No. 199, Donggang West Road Lanzhou City Gansu China 730000
4. Lanzhou University; Key Laboratory of Evidence Based Medicine and Knowledge Translation of Gansu Province; No. 199, Donggang West Road Lanzhou City Gansu China 730000