1. Department of Pediatric Hematology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, China
2. Department of Pediatrics, People’s Hospital of Rizhao, Rizhao, Shandong, China
3. Department of Obstetrics and Gynecology, Maternal and Child Care Service Centre of Zhaoyuan, Zhaoyuan, Shandong, China