Coagulation and Fibrinolysis Parameters in Normal and in Hypertensive Pregnancies

Evaluation of global haemostatic assays and fibrin structure in patients with pre-eclampsia

INTRODUCTION

Haemostatic balance shifted towards hypercoagulability in normal pregnancy is even more pronounced in pre-eclampsia (P-EC). The aim of this study was to analyse haemostatic disturbances and fibrin clot properties in women with pre-eclampsia and to investigate their association with maternal and foetal outcomes.

METHODS

Forty-six pregnant women diagnosed with pre-eclampsia were included in the study, with blood sampling done on the morning following admission to hospital, as well as after delivery (mean duration 4.8 days). Two global haemostatic assays-endogenous thrombin potential (ETP) and assay of overall haemostatic potential (OHP)-were employed, including fibrin clot turbidity measurements and scanning electron microscopy (SEM) of representative samples.

RESULTS

Three thrombin generation parameters (ETP, t_lag and peak height) and OHP were significantly increased in pre-eclampsia compared with controls, whereas overall fibrinolytic potential (OFP-determined as a parameter of the OHP assay) had significantly lower values. Clot lysis time was significantly prolonged in patients with pre-eclampsia. In the pre-eclamptic group after delivery, we observed a significant elevation in the peak height and a reduction in the time to peak and OFP compared with values before delivery. Pre-eclamptic patients with renal complications had significantly higher values for ETP, peak height and D-dimer. Turbidity measurements and SEM revealed dense fibrin structure in patients with pre-eclampsia.

CONCLUSION

Patients with pre-eclampsia have enhanced coagulation and impaired fibrinolysis before, and even after, delivery. In particular, the presence of multi-organ dysfunction, such as renal dysfunction, may be associated with increased thrombin generation in pre-eclampsia.

Hemostatic Abnormalities in Patients With Severe Preeclampsia

Preeclampsia is the most common medical disorder of pregnancy. Early onset preeclampsia is defined as presentation of hypertension and proteinuria before 34 weeks of gestation. Alterations of endothelial cells and fibrin deposition in microvasculature lead to enhanced activation of the coagulation cascade and impaired fibrinolysis associated with multiple organ dysfunctions. Plasma samples were obtained from 50 patients with severe preeclampsia before 34 weeks of gestation and in 61 patients with late preeclampsia. Factor VIIIR:Ag, fibrinogen, D-dimer, and thrombomodulin increased with advanced pregnancy. The platelet count is very important because of the close correlation with the activations parameters of D-dimer and antithrombin. Our results were consistent with activated coagulation and lowering of platelet count in severe cases with early onset preeclampsia. Women who develop early onset preeclampsia characterized a subgroup of patients with more and severe hematologic abnormalities than women with late preeclampsia (after 34 weeks of gestation).

Tissue factor levels and high ratio of fibrinopeptide A:D-dimer as a measure of endothelial procoagulant disorder in pre-eclampsia

To assess coagulation activation and endothelial cell injury in normotensive and pre-eclamptic pregnant women, a comparison was made of plasma levels of tissue factor, fibronectin, fibrinopeptide A and D-dimer. Samples were taken from 50 nonpregnant women, 40 normotensive pregnant women in the third trimester and 27 women with pre-eclampsia after diagnosis and before treatment. High levels of fibrinopeptide A and D-dimer were found in pre-eclamptic women. Moreover, the ratio fibrinopeptide A:D-dimer was much greater in the pre-eclampsia group than in normotensive pregnant women. The levels of fibronectin and tissue factor were also higher in the pre-eclampsia group. The increase of tissue factor levels suggests an alteration of the extrinsic coagulation pathway in pre-eclampsia. The increase of fibrinopeptide A:D-dimer ratio shows that the activation of coagulation is associated with a relative hypofibrinolysis in pre-eclampsia.