1. Department of Spine Surgery, Chengyang District People’s Hospital of Qingdao City, Qingdao 266109, China
2. Department of Gynecology, Chengyang District People’s Hospital of Qingdao City, Qingdao 266109, China
3. Department of Obstetrics, Chengyang District People’s Hospital of Qingdao City, Qingdao 266109, China