The effect of autologous blood donation during the third trimester of pregnancy on the maternal circulation, the properties of blood collected in a phosplatebuffered citrate anticoagulant solution, and the clinical outcome of autologous blood donation and transfusion for pregnant women were investigated in this study. Thirty-four pregnant women with placenta previa or previous cesarean delivery underwent phlebotomies in an autologous transfusion program. Three hundred ml of blood was collected under the observation of fetal heart rate patterns and uterine contractions from 3 weeks prior to the planned date of cesarean section and a total of 900ml of blood was stored. Electronic fetal monitoring tracings were all normal and changes in blood pressure and pulse rates were minimal during the blood donation. The decrease in hemoglobin after the removal of 900ml of blood was only 0.6g/dl on average during the 3 weeks, since the concentration of erythropoietin in serum and the counts of reticlocyte increased in a few days after blood removal. But there were no significant changes in TAT levels in serum. Twelve out of 34 pregnant women received the autologous blood transfusion during or after cesarean delivery and the homologous transfusions were avoided. The results of this study suggested that autologous blood transfusion for pregnant women with a high incidence of blood loss at delivery, such as placenta previa or previous cesarean delivery was safe and advantageous in avoiding homologous blood transfusion.