1. Department of Obstetrics, Yantaishan Hospital, Yantai 264000, Shandong Province, China
2. Department of Obstetrics, Chengyang People’s Hospital, Qingdao 266000, Shandong Province, China
3. Medical Insurance Department, Zhangqiu District People’s Hospital, Jinan,250200, Shandong Province, China
4. Department of Paediatrics (II), Zhangqiu District People’s Hospital, Jinan 250200, Shandong Province, China
5. Department of Clinical Laboratory, Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, Jinan 250013, Shandong Province, China