5Young P,Hamilton R,Hodgett S,et al.Reducing risk by improving standards of intrapartum fetal care[J].J R Soc Med,2001,94(5):226-231.
6Macones GA,Hankins GD,Spong CY,et al.The 2008 National institute of child health and human development workshop report on electronic fetal monitoring:update on definitions,interpretation,and research guidelines[J].Obstet Gynecol,2008,37(5):510-515.
7Strong TH Jr, Elliott JP, Radin TG. Non-coiled umbilical blood vessels:a new marker for the fetus at risk. Obstet Gynecol,1993, 81:409-411.