1. Department of Obstetrics and Gynecology; The Second Hospital of Hebei Medical University; 215 Heping West Road; Shijiazhuang 050000 China
2. Mount Vernon Hospital Affiliated With New York Medical College; 12 N 7th Avenue; Mount Vernon New York 10550
3. Department of Obstetrics and Gynecology; Hospital of Hebei University; 213 Yuhua East Road; Baoding 071000 China
4. Department of Pharmacology; Hebei Medical University; 361 Zhongshan East Road; Shijiazhuang 050000 China