1. Reproductive Medicine Center of The First Hospital of Lanzhou University, Lanzhou, China
2. Key Laboratory of Reproductive Medicine and Embryology of Gansu Province, Lanzhou, China
3. Department of Anesthesiology, Gansu Provincial Hospital, Lanzhou, China
4. School of Medicine, Northwest Minzu University, Lanzhou, China
5. Department of Foreign Exchange and Cooperation, Gansu Provincial Hospital, Lanzhou, China