1. Department of Obstetrics and Gynecology; Union Hospital; Tongji Medical College; Huazhong University of Science and Technology; Wuhan China
2. Department of Obstetrics and Gynecology; Jingzhou First Hospital; Yangtze University; Jingzhou China
3. Department of Obstetrics and Gynecology; Renhe Hospital; China Three Gorges University; Yichang China