1. Department of Obstetrics and Gynecology, Gezhouba Central Hospital of Sinopharm, China Three Gorges University, Yichang, Hubei, P.R. China
2. Department of Obstetrics and Gynecology, The Third Clinical Medical College of China, Three Gorges University, Gezhouba Central Hospital of Sinopharm, Yichang, Hubei, P.R. China