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Smmary: The effect of pregnancy on the components of the fibrinolytic enzyme system was determined by serial observations on 10 healthy women during normal pregnancy, labour, and the puerperium. The The haemostatic mechanism in pregnancy appears to be altered towards an enhanced capacity to form fibrin and a diminished ability to lyse fibrin. These changes may be a physiological development to ensure the integrity of the foetal and maternal circulations and provide rapid and effective haemostasis in the uterus during and after placental separation. Nevertheless, the changes may also establish a vulnerable state for intravascular fibrin deposition. Introduction The fibrinolytic enzyme system or plasminogen-plasmin system has a physiological role complementary to the coagulation mechanism in maintaining the patency of the blood vessels by promoting the removal of intravascular fibrin. The behaviour of the fibrinolytic mechanism in human pregnancy is therefore of special interest because an increase in the concentration of certain coagulation factors, particularly fibrinogen, is known to occur as pregnancy advances. Fibrinolytic activity has been reported to be decreased in late pregnancy, but many of the previous reports are single observations obtained under varying conditions and conflicting results have been presented. The purpose of this investigation was to elucidate the changes in the components of the fibrinolytic enzyme system induced by pregnancy and parturition by serial observations on a group of healthy women followed throughout normal pregnancy, labour, and the puerperium.According to current concepts the coagulation and fibrinolytic systems may be in a state of dynamic equilibrium which keeps the vascular compartment intact and patent, the coagulation system laying down fibrin on the vascular endothelium to seal any gaps which may occur, and the fibrinolytic system removing such fibrinous deposits after they have served their

SummaryThe coagulation and fibrinolytic mechanisms were investigated in a group of patients with severe pre-eclampsia and eclampsia and the findings were compared with those of healthy women in late pregnancy. In patients with pre-eclampsia the following significant differences were found: (1) greater depression of plasma fibrinolytic activity (euglobulin lysis time) than in normal pregnancy, (2) a higher level of inhibitor to urokinaseinduced lysis, (3) increased levels of serum fibrin degradation products, and (4) reduced platelet counts.In patients with eclampsia a progressive increase of the level of serum fibrin degradation products was found over the three days following eclamptic seizures. No such increase occurred after grand mal seizures in late pregnancy. The findings in this study support the view that intravascular clotting is taking place in pre-eclampsia and that this disturbance of the balance between coagulation and fibrinolysis may be localized to certain areas of the vascular compartment, particularly the placental and renal circulations. Fibrin deposition in the maternal vessels supplying the placenta would impair the placental blood flow, which may explain the placental insufficiency which occurs in pre-eclampsia. Likewise fibrin deposition in the renal vasculature will result in glomerular damage and proteinuria. Hypertension may be related to the renal

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Summary: A detailed sequential study of the coagulation and fibrinolytic systems in 15 healthy women during normal childbirth showed that striking changes in keeping with activation of the clotting mechanism take place during and after placental separation. Shortening of the clotting-test results, a sharp increase of factors VIII and V, and a decrease of the plasma fibrinogen were found as the placenta separated. Within one hour of normal delivery the levels of fibrin/fibrinogen degradation products increased and fibrinolytic activity returned to normal non-pregnant levels. In the early puerperium a secondary increase took place in the plasma fibrinogen level, factor VIII remained raised, and the platelet count showed a pronounced rise; these changes may explain the increased predisposition to thromboembolic complications in the puerperium. IntroductionNormal pregnancy is accompanied by major changes in the haemostatic mechanism, particularly an increase in the levels of certain coagulation factors-for example, factors VII, VIII, and X-and fibrinogen and a pronounced decrease in fibrinolytic activity. Parturition presents a serious challenge to the integrity of the vascular compartment, but it has been generally held (Taylor, 1966;Donald, 1969) that contraction of the myometrium-the "living ligatures" of the uterus-is the mechanism which, in the main, controls blood loss at delivery. In other situations where there is injury to the vascular tree an efficient blood coagulation system plays a vital part in achieving effective haemostasis and preserving the blood volume. The purpose of this investigation was to determine the effect of parturition on the haemostatic mechanism by a detailed sequential study of the coagulation and fibrinolytic systems during and after the actual process of normal childbirth and placental separation.The coagulation and fibrinolytic mechanisms may be in a state of dynamic equilibrium which keeps the vascular compartment intact and patent, the coagulation system laying down fibrin to seal any gaps in the vascular endothelium and the fibrinolytic mechanism removing the deposits of fibrin after they have served their haemostatic function (McNicol and Douglas, 1964). A reflection of in-vivo events may therefore be obtained by simultaneous study of the dual mechanisms of blood coagulation and fibrinolysis.

Summary Tests of coagulation, fibrinolysis and platelet function were performed in patients with normal pregnancy, severe pre‐eclampsia, mild pre‐eclampsia, essential hypertension and placental insufficiency. Compared with normal pregnancy, severe pre‐eclampsia was associated with higher serum and urinary fibrinolytic degradation products, cryofibrinogen and factor VIII levels, lower plasminogen and antithrombin activity and diminished sensitivity to urokinase‐induced fibrinolysis. In addition severely pre‐eclamptic patients had reduced platelet counts, lower response to adenosine diphosphate platelet aggregation and diminished platelet factor 3 activity. These changes were present before delivery and in the immediate puerperium, but six weeks after delivery the only difference detected between severely pre‐eclamptic and normal patients was reduced platelet disaggregation in the severely pre‐eclamptic group. In mild pre‐eclampsia the changes in coagulation and fibrinolysis were less marked but serum fibrinolytic degradation products, cryofibrinogen, factor VIII and V levels were significantly raised and the platelet count reduced. No abnormalities of coagulation, fibrinolysis or platelet function were detected in essential hypertension. In placental insufficiency there was diminished platelet disaggregation before delivery but all other tests of coagulation, fibrinolysis and platelet function were similar to normal pregnancy. These results support the hypothesis that intravascular coagulation is present in pre‐eclampsia.

SummaryPlatelet counts, coagulation factors, and the fibrinolytic system were studied in seven regular dialysis patients during the course of haemodialysis by parallel flow (Gambro-Alwall) and coil (Travenol Ultra-Flo 100) dialysers. Significant falls in the patients' platelet counts and rises in their factor V levels were found with both dialysis systems. The changes were more pronounced over the course of a Gambro-Alwall dialysis, when significant falls in the partial thromboplastin clotting time and in the plasminogen levels were also noted. These haemostatic changes were associated with the retention of platelets on the dialysis membranes and, in the case of the Gambro-Alwall dialyser, with the formation of plateletfibrin thrombus. This thrombus formation may take place in spite of efficient heparin anticoagulation and may cause excessive blood loss to the regular dialysis patient.

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