1. Department of Women Health Care, Zhangqiu Maternity and Child Care Hospital, Jinan 250200, China
2. Department of Women Health Care, Yantaishan Hospital, Yantai 264000, China
3. Department of Obstetrics and Gynecology, Zhangqiu District People’s Hospital, Jinan 250200, China
4. Medical Insurance Department, Zhangqiu District People’s Hospital, Jinan 250200, China
5. Health Care Department, Zhangqiu Maternity and Child Care Hospital, Jinan 250200, China