1. Department of Clinical Laboratory, The Fourth Hospital of Shijiazhuang, Shijiazhuang, China
2. Department of Anesthesiology, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
3. Department of Obstetrics and Gynecology, The Fourth Hospital of Shijiazhuang, Shijiazhuang, China
4. Department of Clinical Laboratory, Hebei Maternity Hospital, Shijiazhuang, China.