Antithrombin III in normal pregnancy

Physiological changes of pregnancy and the Swansea criteria in diagnosing acute fatty liver of pregnancy

The Swansea criteria are used to assess the likelihood of acute fatty liver of pregnancy. There are significant physiological changes in normal pregnancy in several of the pathology parameters used in the Swansea criteria. This may impact the sensitivity and specificity of the Swansea criteria. Five of the 11 case series reporting laboratory values in acute fatty liver of pregnancy used values divergent from the Swansea criteria. When using the Swansea criteria for diagnosis of acute fatty liver of pregnancy, using pregnancy-specific and/or laboratory-specific reference intervals is recommended. Simpler diagnostic criteria using parameters of hepatocellular damage and hepatic synthetic dysfunction may be an alternative to the Swansea criteria, and further studies investigating the sensitivity and specificity of these parameters would be useful.

Review article: Investigations and the pregnant woman in the emergency department - part 1: Laboratory investigations

Accurate assessment of the pregnant patient in the ED depends on knowledge of physiological changes in pregnancy, and how these changes may impact on pathology tests, appearance on point-of-care ultrasound and electrocardiography. In addition the emergency physician needs to be cognisant of disorders that are unique to or more common in pregnancy. Part 1 of this review addresses potential deviations in laboratory investigation reference intervals resulting from physiological alterations in pregnancy, and the important causes of abnormal laboratory results in pregnancy. Part 2 will address the role of point-of-care ultrasound in pregnancy, physiological changes that may affect interpretation of point-of-care ultrasound, physiological changes in electrocardiography, and the safety of radiological procedures in the pregnant patient.

Global hemostasis in healthy bitches during pregnancy and at different estrous cycle stages: Evaluation of routine hemostatic tests and thromboelastometry

This study assessed the global hemostasis (including prothrombin time [PT], activated partial thromboplastin time [aPTT], antithrombin activity [ATA], fibrinogen and d-Dimer concentrations, platelet count, plateletcrit and thromboelastometry) in healthy pregnant bitches, comparing the results with those of healthy bitches at different estrous cycle stages, and assessed whether hemostatic changes during pregnancy are associated with serum progesterone concentration or the presence of fetuses in utero. The results show that pregnant bitches have higher fibrinogen concentration, platelet count and platelatecrit, and that fibrin and global clot formations occur faster than in non-pregnant bitches at different estrous cycle stages. Additionally, clot strength was higher in pregnant bitches than in non-pregnant ones. There were no differences in PT, ATA, and D-dimer concentration between all study groups. The aPTT was significantly shorter in bitches at the fourth and last pregnancy weeks, compared to the anestrus group, and shorter in both the fourth and last pregnancy weeks groups, compared to diestrus group. These results all support a hypercoagulable state in healthy pregnant bitches, unassociated with progesterone concentration.

HELLP syndrome in pregnancies below 26th week

OBJECTIVE

To test the hypothesis that HELLP syndrome may be more likely to develop earlier, if a pregnant woman has aPL antibodies, and to observe clinical and laboratory factors preceding the occurrence of HELLP syndrome.

MATERIALS AND METHODS

The study consisted in retrospective analysis, with updated verification, of HELLP syndrome in pregnancies below 26th week in our clinic in the years 1992-2010.

RESULTS

HELLP syndrome, if it occurred before the 26th week, occurred only in women with preeclampsia superimposed on chronic hypertension and in women with aPL antibodies. HELLP syndrome with aPL antibodies occurred with low level of platelets (mean 35.5 × 10(9)/L), lower level of AT III (mean 71.3%), lymphopenia, higher CRP (mean 9.1) and pale infarct of placenta (100%). The occurrence of HELLP syndrome was always preceded by surges in blood pressure resistant to antihypertensive drugs.

CONCLUSION

HELLP syndrome in early pregnancy may indicate the presence of aPL antibodies. It may also be a clinical symptom of APS. A surge in blood pressure is a clinical forerunner of the coming HELLP syndrome. HELLP syndrome in women with APS is characterized by low level of platelets.

A successful outcome of pregnancy in a patient with congenital antithrombin deficiency

BACKGROUND

Presence of inherited thrombophilia is an additional risk factor for maternal thromboembolism and certain adverse pregnancy outcomes, including recurrent fetal loss, placental abruption, intrauterine growth restriction and early-onset severe preeclampsia. Pregnant women with thrombophilia, especially those with antithrombin (AT) deficiency, are at high risk of both kinds of complications.

CASE REPORT

We presented a pregnant women with congenital antithrombin deficiency in the first pregnancy, whose mother had had four times pregnancy-related deep vein thrombosis, and antithrombin deficiency. With the regular laboratory monitoring of hemostatic parameters and gynaecology surveillance including the follow-up of placental vascular flow, the whole pregnancy proceeded without complications. The prophylactic therapy with low molecular weight heparin was introduced from the 20th week of gestation and one dose of substitution therapy with antithrombin concentrate was administrated before delivery. Pregnancy and labour were terminated without complications at the 37th week of gestation, resulting in the delivery of a healthy male newborn of 3.6 kg body weight, 52 cm long, and with the Apgar scores of 9/10.

CONCLUSION

A timely made diagnosis of thrombophilia, accompanied with regular obstetrics check-ups and follow-ups of hemostatic parameters during pregnancy, as well as the use of adequate prophylactic and substitution therapy, are the successful tools for the prevention of possible maternal complications and pregnancy itself in our patient with congenital AT deficiency.

Haemostatic changes in pregnancy

Normal pregnancy is accompanied by changes in the coagulation and fibrinolytic systems. These include increases in a number of clotting factors (I, II, VII, VIII, IX and XII), a decrease in protein S levels and inhibition of fibrinolysis. As gestation progresses, there is also a significant fall in the activity of activated protein C, an important anticoagulant. While these physiological changes may be important for minimizing intrapartum blood loss, they entail an increased risk of thromboembolism during pregnancy and the post-partum period.

Interaction of the protein C/protein S anticoagulant system, the endothelium and pregnancy

Normal pregnancy is associated with significant changes in haemostasis, lipid metabolism and endothelial function. This suggests that maternal adaptation in these systems is required for successful pregnancy outcome. A number of acquired and heritable prothrombotic abnormalities are associated with complications in pregnancy. A common feature of these abnormalities is their ability to alter endothelial function or the protein C/protein S system and increase thrombin generation. In this review the normal function of the endothelium and the protein C/protein S system is detailed. The changes which characterize normal and complicated pregnancies are outlined and the evidence for the impact of heritable and acquired disorders of the protein C/protein S system on pre-eclampsia and fetal loss are discussed.

Coagulation and fibrinolysis in smoking and nonsmoking pregnant women

OBJECTIVES

To assess the effects of smoking during pregnancy on coagulation and fibrinolysis.

DESIGN

A cross-sectional study.

SETTING

A teaching hospital in Heerlen, The Netherlands.

RESULTS

Parameters of coagulation activation increased significantly with gestational age. The values presented are median values. Prothrombin fragment 1 + 2 increased from 0.8 to 2.5 nmol/l in the nonsmoking group of pregnant women and from 1.0 to 1.8 nmol/l in the smoking group. Thrombin-antithrombin III (TAT) levels increased from 2.2 to 9.9 micrograms/l in the nonsmoking group and from 3.1 to 8.5 micrograms/l in the smoking group. Parameters of fibrinolysis showed a different picture. Plasminogen levels in both groups rose significantly in the first half of gestation reaching a plateau in the second half. The alpha 2-antiplasmin levels remained constant in both groups, although the smokers started with significantly higher levels: 119 versus 105% in the nonsmokers. The D-dimer levels rose significantly in both groups: from 278 to 847 micrograms/ml in the nonsmokers and from 215 to 520 micrograms/ml in the smokers. They were significantly lower in the smoking group from the 11th up to the 40th weeks. The D-dimer/TAT ratio was significantly higher in the nonsmokers.

CONCLUSIONS

In smoking pregnant women the activated coagulation process was not counter balanced by an adequate increase of fibrinolysis which was the case in the nonsmokers.

Hemostatic parameters and platelet activation by flow-cytometry in normal pregnancy: a longitudinal study

Nineteen pregnant women with uncomplicated pregnancies were studied during the first, second, and third trimesters. We measured the following hemostatic parameters: prothrombin time, activated partial thromboplastin time, fibrinogen, antithrombin III, protein C, protein S, platelet number and volume. Platelet function was examined by a cytofluorimetric method, using an anti-GPM-140 antibody which is directed against a platelet alpha granule membrane protein. Activated platelets were expressed as a percentage of the GMP-140-positive platelets over total platelets. Fibrinogen levels showed a steady increase during pregnancy; conversely prothrombin time, activated partial thromboplastin time, protein C, and antithrombin III showed no significant modifications and remained within the reference range. There was a decrease of protein S activity throughout pregnancy, although protein S antigen did not follow this trend. The decrease occurred early in pregnancy and persisted during the second and third trimesters, reaching a stable plateau. We observed no platelet volume change or activation: the percentage of activated platelets was within the normal reference range, even in late pregnancy.

The value of antithrombin-III and fibronectin in hypertensive disorders of pregnancy

In this study we evaluated fibronectin as a marker of endothelial cell injury and antithrombin III as a marker of chronic activation of intravascular coagulation. The aim of the study was to establish to normal trends of plasma antithrombin III and fibronectin in general obstetric population and to determine the value of both in predicting, distinguishing and understanding the pathophysiology of pregnancy induced hypertension. The all cases consisted of 173 pregnant, 19 of them were chronic hypertensive, 45 were pregnancy induced hypertensive and 119 were normotensive at blood sampling. Out of 119 normotensive cases, 109 cases had no adverse outcome during their pregnancy. These cases were used as a control group and for the normal trends of antithrombin III and fibronectin in general obstetric population. Ten out of 119 cases who developed preeclampsia during follow up, 19 cases with chronic hypertension and 45 cases with pregnancy induced hypertension consisted of the study group. In the cases who developed preeclampsia during follow up, the value of plasma fibronectin level (above 95% confidence limit for that gestational week) to predict preeclampsia had 90% sensitivity and 94.4% specificity. In distinguishing hypertensive disorders of pregnancy (chronic hypertension or pregnancy induced hypertension) fibronectin had 71.1% sensitivity and 100% specificity. Plasma antithrombin III level (of antigenicity) measured by immunodiffusion method had no value in predicting and distinguishing pregnancy induced hypertension.

Evaluation of the haemostatic profile in the pre- and post parturient mare, with particular focus on the perinatal period

Various haemostatic analytes were systematically evaluated for four months pre-partum and five months post partum in 14 healthy mares. The plasma fibrinogen concentration and both Factor VIII:C and von Willebrand factor activity showed gradual increases from mid-gestation and reached maximal, or near maximal activity at parturition. These increases were paralleled by an increase in plasma fibronectin concentration, the appearance of fibrinogen degradation products, and a modest rise in antithrombin III concentration. In contrast, the activity of Factor VII and Factor IX, and the one-stage prothrombin (PT) time and the activated partial thromboplastin (APTT) time remained relatively constant throughout the pre- and post parturient period.

Management of thrombophilia in pregnancy

Thromboembolism remains a major cause of maternal morbidity and mortality. The incidence of thrombosis associated with pregnancy is stated to be around 0.09%1 but is greater in women with familial or acquired thrombophilia. Around 50% of pregnancies in women with antithrombin III deficiency are complicated by thrombosis. Anticoagulation throughout pregnancy and the puerperium is recommended in women with antithrombin III deficiency. Because thrombosis is less common in women with protein C or protein S deficiency less aggressive management may be appropriate during pregnancy but anticoagulation post partum is generally recommended. The most important acquired thrombophilic abnormality is the development of antiphospholipid antibodies ('lupus anticoagulants'). Women with these antibodies may present major problems but no clear guidelines for their management currently exist. The majority of women with a history of thrombosis have no identifiable haemostatic abnormality. Management of pregnancy in these patients depends on individual circumstances.

Thrombin-antithrombin III complex levels in normal pregnancy with hypertensive disorders and after delivery

The plasma concentration of the thrombin-antithrombin III-complex (TAT) was investigated during uncomplicated pregnancy in 15 women in the first, 22 in the second and 46 in the third trimester, and in 19 women with hypertensive disorders between 25 and 40 weeks gestation. Eight women at term after a normal pregnancy were studied before the onset of labour and within 60 min and 24 h after delivery. A comparison group of 16 healthy, non-pregnant women was investigated. The mean TAT concentration in normal pregnancies increased significantly in the second and third trimester compared with values in the first trimester and in non-pregnant women. In the group with hypertensive disorders during pregnancy TAT levels were significantly higher than in uncomplicated pregnancies. Within 60 min after delivery a distinct increase of TAT concentrations occurred compared to levels before the onset of labour but the levels had returned to normal by 24 h after delivery. Our findings suggest that an activation of the coagulation system occurs in normal pregnancy. A further activation takes place immediately after delivery. The significantly increased TAT levels in pregnancies with hypertensive disorders suggest a state of chronic disseminated intravascular coagulation leading to an enhanced consumption of and a decreased plasma concentration of antithrombin III.

Enhanced thrombin generation in normal and hypertensive pregnancy

We investigated the plasma levels of thrombin-antithrombin III complexes in women with uncomplicated pregnancy, patients with preeclampsia, gestational hypertension, and nonpregnant control subjects. In addition, we measured the coagulation inhibitors antithrombin III, protein C, and protein S. In normal pregnancy we observed a progressive increase in plasma thrombin-antithrombin III levels, and a decrease in protein S levels. In preeclampsia we observed increased thrombin-antithrombin III levels, reduced antithrombin III and protein C levels, and no further reduction of protein S compared with normal pregnancy. These new methods provide solid evidence for a prethrombotic state in normal pregnancy, especially in preeclampsia.

Plasma antithrombin III levels in pre-eclampsia and chronic hypertension

Plasma levels of antithrombin III were tested during pregnancy in a control group of normal patients and in a study group that included patients with moderate and severe pre-eclampsia and chronic hypertension. The control group showed mean antithrombin III activity of 97.9 +/- 20.9%, the severe pre-eclamptic patients 22.33 +/- 18.22%, the moderate pre-eclamptic patients 56.0 +/- 7.56%, and the chronic hypertensive patients 77.5 +/- 6.69%. The difference between normal pregnancy and moderate pre-eclampsia was significant at P less than 0.002, normal pregnancy and severe pre-eclampsia P less than 0.002, moderate and severe pre-eclampsia P less than 0.002, chronic hypertension and normal pregnancy P less than 0.1, and chronic hypertension and severe pre-eclampsia P less than 0.002. All the severe pre-eclamptic patients and 2 out of 6 of the moderate pre-eclamptic women were below 55.7% (mean - 2S.D.) of normal antithrombin III activity. Patients with heavy proteinuria had depressed antithrombin III activity. However, chronic hypertensive pregnancies, although rather a small group, had almost normal values of plasma antithrombin III activity. The plasma antithrombin III value may thus help to distinguish between chronic hypertension and severe pre-eclamptic disease.

Platelet function and coagulation in normal and preeclamptic pregnancy

Platelet function and coagulation activity were followed prospectively throughout normal pregnancy and in puerperium in 17 healthy women. Plasma beta-thromboglobulin reflecting platelet activation increased progressively during pregnancy. This was not accompanied by any changes in platelet count or lifespan nor in serum or plasma thromboxane B2 levels. The levels of both factor VIII:C and factor VIIIR:Ag increased, the former less than the latter resulting in a rise of the FVIIIR:Ag/FVIII:C ratio. Antithrombin III (AT III), however remained unaltered. FVIIIR:Ag/FVIII:C ratio was increased both in mild (n = 7) and severe (n = 9) preeclampsia, whereas beta-thromboglobulin was increased and AT III was decreased only in severe preeclampsia. Platelet count and lifespan, plasma and serum thromboxane B2 as well as FVIII:C were normal in severe preeclampsia.

Heparin cofactor activity and antithrombin III antigen levels in preeclampsia

It has been reported that patients with preeclampsia have decreased levels of antithrombin III heparin cofactor and that the degree of depression parallels the severity of disease. To determine the time course of development and resolution of this deficiency, and to gain insight into the cause of this deficiency, plasma antithrombin III antigen and heparin cofactor activity levels were measured serially in 11 women with mild preeclampsia. Although the ATIII antigen level remained stable during the antepartum period, the level of heparin cofactor was noted to fall progressively during the antepartum period. Both ATIII antigen and heparin cofactor increased promptly postpartum. The discrepancy between the levels of ATIII antigen and heparin cofactor activity suggests that in both mild and severe preeclampsia there is utilization of antithrombin III to form inactive protease inhibitor complexes.

Antithrombin III levels in preeclampsia correlate with maternal and fetal morbidity

In 57 patients with pregnancy-induced or aggravated hypertension, antithrombin III levels correlated inversely with maternal morbidity. Morbidity was determined by the maximal diastolic blood pressure, disturbance of renal and liver function, and thrombocytopenia. Antithrombin III levels and platelet counts correlated inversely with the degree of placental infarction. Proteinuria (grams per 24 hours) was most predictive of fetal outcome, which was considered to be either favorable if a healthy baby could be discharged with its mother or unfavorable in case of perinatal death or a prolonged stay in the neonatal intensive care unit. Plasma antithrombin III and serum glutamic oxaloacetic transaminase levels, in that order, augmented the number of correct predictions. Antithrombin III inhibits blood coagulation by forming irreversible complexes with activated clotting enzymes, notably with factor Xa and thrombin. Evidence is presented which suggests that antithrombin III levels in preeclampsia are depressed as a result of increased consumption in the maternal vascular tree, rather than decreased synthesis or increased urinary loss.

Pregnancy-associated plasma protein-A (PAPP-A) inhibits thrombin-induced coagulation of plasma

Concentrations of immunoreactive PAPP-A have been found significantly lower in the serum as compared to heparin or EDTA plasma from the same patients. After coagulation significant amounts of PAPP-A remain associated with the clot. Purified PAPP-A inhibits thrombin induced coagulation of plasma. This inhibition cannot be attributed to a direct effect of PAPP-A on thrombin. It is exerted via an activation of endogenous antithrombin III since the inhibitory effect of PAPP-A on thrombin induced coagulation in a euglobulin system can be observed only if antithrombin III is added. The fact that protamine sulphate is capable of neutralizing the inhibitory effects of PAPP-A made us postulate that PAPP-A, like heparin, possesses strongly acidic residues which bind to protamine.

Plasma antithrombin III levels in pre-eclampsia

In a prospective study plasma AT III was determined in 2423 samples obtained from 653 women during pregnancy and post partum. The women were allocated to groups, according to the highest diastolic blood pressure, in the third trimester. AT III levels were normal throughout pregnancy, during labour and after vaginal delivery, except in 57 women with pregnancy induced or aggravated hypertension. We present evidence that AT III depression in pre-eclampsia is caused by increased consumption. AT III levels correlate with maternal morbidity as revealed by hepatorenal damage. A weak but significant correlation of AT III and platelets with placental infarction was demonstrated. Proteinuria was the best predictor of fetal outcome. AT III plasma levels increased the number of correct predictions. Following vaginal delivery AT III plasma levels rapidly returned to normal values.