1. Delivery Room, Zhangqiu District Maternal and Child Health Care Hospital, Jinan, Shandong 250200, P.R. China
2. Department of Nursing, Zhangqiu District Maternal and Child Health Care Hospital, Jinan, Shandong 250200, P.R. China
3. Department of Obstetrics, The People's Hospital of Zhangqiu Area, Jinan, Shandong 250200, P.R. China
4. Department of Endocrinology, The People's Hospital of Zhangqiu Area, Jinan, Shandong 250200, P.R. China
5. Department of Personnel, The People's Hospital of Zhangqiu Area, Jinan, Shandong 250200, P.R. China
6. Department of Obstetrics, East Hospital of Tongji University, Shanghai 200120, P.R. China