3The Canadian Task Force on the Periodic Health Examination -The Canadian Guide to Clinical Preventive Health Care[S].Health Canada,1994
4Kwast BE.Postpartum haemorrhage:its contribution to maternal mortality[J].Midwifery,1991,7:64-70
5World Health Organization.Maternal mortality:A Global Factbook[R].Geneva,WHO 1991b
6Berg CJ,Atrash HK,Tucker M.Pregnancy-related mortality in the United States,1987-1990[J].Obstet Gynecol,1996,88:161-167
7Rochat RW,Koonin LM,Atrash HK,et al.The maternal mortality collaborative maternal mortality in the United States:report from the maternal mortality collaborative[J].Obstet Gynecol,1972,91:91-97
8Department of Health.Why Mothers Die.Report on confidential inquiries into maternal deaths in the United Kingdom1994/96[R].London:Her Majesty's Stationery Office,1998
9Pritchard JA,Baldwin RM,Dickey JC,Wiggins KM.Blood volume changes in pregnancy and the puerperium[J].Am J Obstet Gynecol,1962,84:1271-1282