Tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in amniotic fluid and blood plasma: implications for the mechanism of amniotic fluid embolism

Tissue Factor Pathway Inhibitors as Potential Targets for Understanding the Pathophysiology of Preeclampsia

BACKGROUND

Preeclampsia is a hypertensive disorder of pregnancy that causes maternal and perinatal morbidity and mortality worldwide. Preeclampsia is associated with complex abnormalities of the coagulation and fibrinolytic system. Tissue factor (TF) is involved in the hemostatic system during pregnancy, while the Tissue Factor Pathway Inhibitor (TFPI) is a major physiological inhibitor of the TF-initiated coagulation cascade. The imbalance in hemostatic mechanisms may lead to a hypercoagulable state, but prior research has not comprehensively investigated the roles of TFPI1 and TFPI2 in preeclamptic patients. In this review, we summarize our current understanding of the biological functions of TFPI1 and TFPI2 and discuss future directions in preeclampsia research.

METHODS

A literature search was performed from inception to 30 June 2022 in the PubMed and Google Scholar databases.

RESULTS

TFPI1 and TFPI2 are homologues with different protease inhibitory activities in the coagulation and fibrinolysis system. TFPI1 is an essential physiological inhibitor of the TF-initiated extrinsic pathway of coagulation. On the other hand, TFPI2 inhibits plasmin-mediated fibrinolysis and exerts antifibrinolytic activity. It also inhibits plasmin-mediated inactivation of clotting factors and maintains a hypercoagulable state. Furthermore, in contrast to TFPI1, TFPI2 suppresses trophoblast cell proliferation and invasion and promotes cell apoptosis. TFPI1 and TFPI2 may play important roles in regulating the coagulation and fibrinolytic system and trophoblast invasion to establish and maintain successful pregnancies. Concentrations of TF, TFPI1, and TFPI2 in maternal blood and placental tissue are significantly altered in preeclamptic women compared to normal pregnancies.

CONCLUSIONS

TFPI protein family may affect both the anticoagulant (i.e., TFPI1) and antifibrinolytic/procoagulant (i.e., TFPI2) systems. TFPI1 and TFPI2 may function as new predictive biomarkers for preeclampsia and navigate precision therapy.

Procoagulant Activity in Amniotic Fluid Is Associated with Fetal-Derived Extracellular Vesicles

Procoagulant activity in amniotic fluid (AF) is positively correlated with phosphatidylserine (PS) and tissue factor (TF)-expressing(+) extracellular vesicles (EVs). However, it is unknown if pathological fetal conditions may affect the composition, phenotype, and procoagulant potency of EVs in AF. We sought to evaluate EV-dependent procoagulant activity in AF from pregnant people with fetuses with or without diagnosed chromosomal mutations. AF samples were collected by transabdominal amniocentesis and assessed for common karyotype defects (total n = 11, 7 healthy and 4 abnormal karyotypes). The procoagulant activity of AF was tested using a fibrin generation assay with normal pooled plasma and plasmas deficient in factors XII, XI, IX, X, V, and VII. EV number and phenotype were determined by flow cytometry with anti-CD24 and anti-TF antibodies. We report that factor-VII-, X-, or V-deficient plasmas did not form fibrin clots in the presence of AF. Clotting time was significantly attenuated in AF samples with chromosomal mutations. In addition, CD24+, TF+, and CD24+ TF+ EV counts were significantly lower in this group. Finally, we found a significant correlation between EV counts and the clotting time induced by AF. In conclusion, we show that AF samples with chromosomal mutations had fewer fetal-derived CD24-bearing and TF-bearing EVs, which resulted in diminished procoagulant potency. This suggests that fetal-derived EVs are the predominant source of procoagulant activity in AF.

DIC in Pregnancy - Pathophysiology, Clinical Characteristics, Diagnostic Scores, and Treatments

Obstetrical hemorrhage and especially DIC (disseminated intravascular coagulation) is a leading cause for maternal mortality across the globe, often secondary to underlying maternal and/or fetal complications including placental abruption, amniotic fluid embolism, HELLP syndrome (hemolysis, elevated liver enzymes and low platelets), retained stillbirth and acute fatty liver of pregnancy. Various obstetrical disorders can present with DIC as a complication; thus, increased awareness is key to diagnosing the condition. DIC patients can present to clinicians who may not be experienced in a variety of aspects of thrombosis and hemostasis. Hence, DIC diagnosis is often only entertained when the patient already developed uncontrollable bleeding or multi-organ failure, all of which represent unsalvageable scenarios. Beyond the clinical presentations, the main issue with DIC diagnosis is in relation to coagulation test abnormalities. It is widely believed that in DIC, patients will have prolonged prothrombin time (PT) and partial thromboplastin time (PTT), thrombocytopenia, low fibrinogen, and raised D-dimers. Diagnosis of DIC can be elusive during pregnancy and requires vigilance and knowledge of the physiologic changes during pregnancy. It can be facilitated by using a pregnancy specific DIC score including three components: 1) fibrinogen concentrations; 2) the PT difference - relating to the difference in PT result between the patient's plasma and the laboratory control; and 3) platelet count. At a cutoff of ≥26 points, the pregnancy specific DIC score has 88% sensitivity, 96% specificity, a positive likelihood ratio (LR) of 22, and a negative LR of 0.125. Management of DIC during pregnancy requires a prompt attention to the underlying condition leading to this complication, including the delivery of the patient, and correction of the hemostatic problem that can be guided by point of care testing adjusted for pregnancy.

Hemostatic parameters in patients with spinal cord injury in subacute and chronic phase of the rehabilitation

Objective: The goal of this study was to measure hemostatic markers after SCI.Design: Assesing changes in coagulation and fibrynilitic system in SCI patients in different time post injury to Cross-sectional study.Setting: Rehabilitation Department of the Bydgoszcz University Hospital, Poland from 2011 to 2017.Participants: SCI patient during acute and chronic rehabilitation (N = 88).Outcome Measures: Assesing following parameters: platelet counts and levels of D-dimer, antithrombin III (ATIII), tissue factor (TF), tissue factor pathway inhibitor (TFPI) and the inflammatory marker, C-reactive protein (CRP).Interventions: Eighty-eight SCI patients were divided into three groups based on the time elapsed from injury: group I (three weeks to three months), group II (three to twelve months) and group III (more than twelve months). All patients underwent ultrasonography (US) to detect acute or chronic recanalized deep vein thrombosis (DVT). Platelet counts and levels of D-dimer, ATIII, TF, TFPI and CRP were assessed. TF and TFPI levels were measured in the control group of forty healthy individuals without SCI, the rest of the parameters were compared to laboratory norms.Results: D-dimer levels were significantly higher in group I compared to group II (P = .0002) and group III (P < .001). Group II had higher D-dimer levels than group III (P = .032). TFPI levels were higher in group II compared with group III (P = .0041) and control group (P = .000033). TF was significantly higher in all the SCI groups compared with the control group (P < .001).Conclusions: D-dimer and TF levels were still elevated twelve months after SCI. TF levels were also elevated over 12 months after inury. The results may indicate that sub-acute and even chronic SCI patients have disturbed coagulation and fibrynolitic system.

Molecular Changes on Maternal-Fetal Interface in Placental Abruption-A Systematic Review

Placental abruption is the separation of the placenta from the lining of the uterus before childbirth. It is an infrequent perinatal complication with serious after-effects and a marked risk of maternal and fetal mortality. Despite the fact that numerous placental abruption risk factors are known, the pathophysiology of this issue is multifactorial and not entirely clear. The aim of this review was to examine the current state of knowledge concerning the molecular changes on the maternal–fetal interface occurring in placental abruption. Only original research articles describing studies published in English until the 15 March 2021 were considered eligible. Reviews, book chapters, case studies, conference papers and opinions were excluded. The systematic literature search of PubMed/MEDLINE and Scopus databases identified 708 articles, 22 of which were analyzed. The available evidence indicates that the disruption of the immunological processes on the maternal–fetal interface plays a crucial role in the pathophysiology of placental abruption. The features of chronic non-infectious inflammation and augmented immunological cytotoxic response were found to be present in placental abruption samples in the reviewed studies. Various molecules participate in this process, with only a few being examined. More advanced research is needed to fully explain this complicated process.

Placental abruption as a trigger of DIC in women with HELLP syndrome: a population-based study

BACKGROUND

Disseminated Intravascular Coagulation (DIC) is a life-threatening condition. Hemolysis, Elevated Liver enzymes and Low Platelets (HELLP) syndrome is one of the obstetrical syndromes mostly associated with DIC and thus, high rates of fatal complications. There is a lack of information regarding epidemiologic and clinical characteristics of women who developed HELLP syndrome with and without DIC. Additionally, until now, there is no adapted and widely accepted way to diagnose DIC among pregnant women presenting with HELLP syndrome, despite the evident maternal mortality linked to the disease.

Objectives: (1) Address the gaps in knowledge regarding the prevalence, epidemiologic and clinical characteristics of women with HELLP syndrome who develop DIC; and (2) determine the risk factors for the development of DIC among women with HELLP syndrome.

STUDY DESIGN

This was a population-based retrospective cohort study, including all women who delivered at the Soroka University Medical Center between the years 2001-2017. The study population was divided into three groups: (1) comparison group (n = 207,266 deliveries); (2) HELLP syndrome without DIC (n = 320); (3) HELLP syndrome with DIC (n = 21). The diagnosis of DIC was based on the ICD-9 code as recorded in the obstetrical database of the Soroka University Medical Center. The coding is based on the diagnosis made by the attending physician during hospitalization.

RESULTS

(1) The rate of HELLP syndrome in the study population was 0.16% (341/207,607), of them 6.16% (21/341) had DIC; (2) among patients with HELLP syndrome, those with DIC had a higher median gravidity and parity; (3) a higher rate of severe maternal morbidity including blood product transfusion, placental abruption, eclampsia, acute renal failure and maternal death was observed in those who had HELLP syndrome and DIC compared to those with HELLP syndrome without DIC and the comparison group (p-value <.001 for comparison among the three groups); (4) among women with HELLP syndrome, those with DIC had a longer median PT difference, higher serum creatinine and lower AST as well as ALT median concentrations than those without DIC; (5) patients with HELLP syndrome and DIC had a higher rate of stillbirth and postpartum death than patients in the other groups (p-value <.001 for comparison among the three groups); and (6) placental abruption was an independent risk factor for the development of DIC in women with HELLP syndrome (p-value <.001).

CONCLUSIONS

(1) Among women with HELLP syndrome, those who developed DIC had a higher rate of maternal and neonatal morbidity and mortality than those without DIC; and (2) placental abruption, but not abnormal liver function, was an independent risk factor for the development of DIC in women with HELLP syndrome.

Amniotic fluid embolism-associated coagulopathy: a single-center observational study

INTRODUCTION

Amniotic fluid embolism (AFE) continues to be a rare, enigmatic condition with high maternal mortality. It is characterized by cardiovascular compromise, loss of consciousness or other neurologic symptoms, and coagulopathy. The latter is usually treated according to existing protocols for consumptive coagulopathy.

METHODS

Serial analyses of a panel of hemostaseological parameters were performed in three consecutive cases of AFE that occurred at our institution.

RESULTS

All mothers and neonates survived without major sequelae. Disproportionately low levels of fibrinogen and factor five, and exorbitantly elevated D-dimers were present in all cases, whereas markers of consumptive coagulopathy, platelets and antithrombin in particular, were only slightly reduced.

DISCUSSION

Our results support hyperfibrinolysis as contributing factor of AFE-associated coagulopathy. We, therefore, propose a treatment algorithm which includes early use of tranexamic acid and transfusion of red blood cells and fresh frozen plasma, adding fibrinogen if hemostasis is not readily achieved.

Meta-Analysis of Maternal and Fetal Transcriptomic Data Elucidates the Role of Adaptive and Innate Immunity in Preterm Birth

Preterm birth (PTB) is the leading cause of newborn deaths around the world. Spontaneous preterm birth (sPTB) accounts for two-thirds of all PTBs; however, there remains an unmet need of detecting and preventing sPTB. Although the dysregulation of the immune system has been implicated in various studies, small sizes and irreproducibility of results have limited identification of its role. Here, we present a cross-study meta-analysis to evaluate genome-wide differential gene expression signals in sPTB. A comprehensive search of the NIH genomic database for studies related to sPTB with maternal whole blood samples resulted in data from three separate studies consisting of 339 samples. After aggregating and normalizing these transcriptomic datasets and performing a meta-analysis, we identified 210 genes that were differentially expressed in sPTB relative to term birth. These genes were enriched in immune-related pathways, showing upregulation of innate immunity and downregulation of adaptive immunity in women who delivered preterm. An additional analysis found several of these differentially expressed at mid-gestation, suggesting their potential to be clinically relevant biomarkers. Furthermore, a complementary analysis identified 473 genes differentially expressed in preterm cord blood samples. However, these genes demonstrated downregulation of the innate immune system, a stark contrast to findings using maternal blood samples. These immune-related findings were further confirmed by cell deconvolution as well as upstream transcription and cytokine regulation analyses. Overall, this study identified a strong immune signature related to sPTB as well as several potential biomarkers that could be translated to clinical use.

Tissue factor activity in women with preeclampsia or SGA: a potential explanation for the excessive thrombin generation in these syndromes

OBJECTIVE

The aim of this study was to determine whether the activity of tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in the plasma of women with preeclampsia (PE) and small for gestational age (SGA) neonate differ from that of normal pregnant women and whether they are related to specific placental lesions.

METHODS

This cross-sectional study included the following groups: (1) normal pregnancy (n = 68); (2) PE (n= 128); and (3) SGA (n = 56). Maternal plasma TF and TFPI activity was determined with chromogenic assays.

RESULTS

(1) The median maternal plasma TF activity, but not TFPI activity, differed among the study groups (p < .0001 and p = .4, respectively); (2) patients with PE had a higher median maternal plasma TF activity than women with normal pregnancies (p < .0001) and mothers with SGA fetuses (p = .002); (3) among patients with PE, those with distal villous hypoplasia had a higher median maternal TF activity than those without these placental lesions (p = .018); and (4) following adjustment for confounding variables, maternal plasma TF and TFPI activity were not associated with an SGA neonate.

CONCLUSIONS

Plasma TF activity is higher in women with PE than in those with SGA or normal pregnancies. We propose that these changes may be responsible, at least in part, for the increased in-vivo thrombin generation observed in this obstetrical syndrome.

Disseminated Intravascular Coagulation Syndromes in Obstetrics

Disseminated intravascular coagulation (DIC) is a syndrome that can be initiated by a myriad of medical, surgical, and obstetric disorders. Also known as consumptive coagulopathy, DIC is a common contributor to maternal morbidity and mortality and is associated with up to 25% of maternal deaths. The etiopathogenesis of DIC is complex and currently thought to be initiated by tissue factor or thromboplastin, which is released from trophoblastic or fetal tissue, or maternal decidua or endothelium. Tissue factor activates the coagulation sequence to cause fibrin clotting and its dissolution by the fibrinolysin system. The result of this process can range from mild, clinically insignificant laboratory derangements to marked coagulopathy with bleeding at sites of minimal trauma. Although clinical recognition varies by disease severity, several organizations have attempted to standardize the diagnosis through development of scoring systems. Several important--albeit not necessarily common--obstetric disorders associated with DIC include placental abruption, amniotic fluid embolism, sepsis syndrome, and acute fatty liver of pregnancy. More common disorders include severe preeclampsia, hemolysis, elevated liver enzymes, and low platelet count syndrome, and massive obstetric hemorrhage. Importantly, many of these disorders either cause or are associated with substantive obstetric hemorrhage. Treatment of DIC is centered on two principles. The first is identification and treatment of the underlying disorder. Because many women with consumptive coagulopathy also have massive hemorrhage, the second tenet of treatment is that obstetric complications such as uterine atony or lacerations must be controlled simultaneously with prompt blood and component replacement for a salutary outcome.

Placental vascular pathology and increased thrombin generation as mechanisms of disease in obstetrical syndromes

Obstetrical complications including preeclampsia, fetal growth restriction, preterm labor, preterm prelabor rupture of membranes and fetal demise are all the clinical endpoint of several underlying mechanisms (i.e., infection, inflammation, thrombosis, endocrine disorder, immunologic rejection, genetic, and environmental), therefore, they may be regarded as syndromes. Placental vascular pathology and increased thrombin generation were reported in all of these obstetrical syndromes. Moreover, elevated concentrations of thrombin-anti thrombin III complexes and changes in the coagulation as well as anticoagulation factors can be detected in the maternal circulation prior to the clinical development of the disease in some of these syndromes. In this review, we will assess the changes in the hemostatic system during normal and complicated pregnancy in maternal blood, maternal–fetal interface and amniotic fluid, and describe the contribution of thrombosis and vascular pathology to the development of the great obstetrical syndromes.

DIC score in pregnant women--a population based modification of the International Society on Thrombosis and Hemostasis score

Objectives

The objectives of this study were: 1) To determine the component needed to generate a validated DIC score during pregnancy. 2) To validate such scoring system in the identification of patients with clinical diagnosis of DIC.

Material and Methods

This is a population based retrospective study, including all women who gave birth at the ‘Soroka University Medical Center’ during the study period, and have had blood coagulation tests including complete blood cell count, prothrombin time (PT)(seconds), partial thromboplastin time (aPTT), fibrinogen, and D-dimers. Nomograms for pregnancy were established, and DIC score was constructed based on ROC curve analyses.

Results

1) maternal plasma fibrinogen concentrations increased during pregnancy; 2) maternal platelet count decreased gradually during gestation; 3) the PT and PTT values did not change with advancing gestation; 4) PT difference had an area under the curve (AUC) of 0.96 (p<0.001), and a PT difference ≥1.55 had an 87% sensitivity and 90% specificity for the diagnosis of DIC; 5) the platelet count had an AUC of 0.87 (p<0.001), an 86% sensitivity and 71% specificity for the diagnosis of DIC; 6) fibrinogen concentrations had an AUC of 0.95 (p<0.001) and a cutoff point ≤3.9 g/L had a sensitivity of 87% and a specificity of 92% for the development of DIC; and 7) The pregnancy adjusted DIC score had an AUC of 0.975 (p<0.001) and at a cutoff point of ≥26 had a sensitivity of 88%, a specificity of 96%, a LR(+) of 22 and a LR(−) of 0.125 for the diagnosis of DIC.

Conclusion

We could establish a sensitive and specific pregnancy adjusted DIC score. The positive likelihood ratio of this score suggests that a patient with a score of ≥26 has a high probability to have DIC.

Pathogenesis and management of peripartum coagulopathic calamities (disseminated intravascular coagulation and amniotic fluid embolism)

Acute coagulopathic peripartum calamities are relatively rare but contribute importantly to maternal morbidity and mortality in the Western world. Abruptio placenta, amniotic fluid embolism, and retained fetal or placental material may lead to fulminant intravascular activation of coagulation which results in thromboembolic complications and consumption coagulopathy causing severe hemorrhage. The central underlying pathophysiological pathway in the coagulopathy associated with these syndromes is the occurrence of tissue factor, released from the placenta and amniotic fluid, in the circulation, in combination with low levels of physiological anticoagulant factors during pregnancy. The diagnosis of DIC may be made trough conventional composite scoring systems employing routine coagulation tests, whereas for the diagnosis of amniotic fluid embolism measurement of insulin like growth factor binding protein-1 seems promising. Therapy is aimed at removing the precipitating factor combined with supportive adjunctive treatment options.

Preeclampsia, hypoxia, thrombosis, and inflammation

Reductions in uteroplacental flow initiate a cascade of molecular effects leading to hypoxia, thrombosis, inflammation, and endothelial cell dysfunction resulting in untoward pregnancy outcomes. In this review, we detail these effects and their relationship to preeclampsia (PE) and intrauterine growth restriction (IUGR).

Comparative evaluation of Tissue factor and Thrombomodulin activity changes during normal and idiopathic early and late foetal loss: the cause of hypercoagulability?

Various components of the coagulation and fibrinolytic pathways are involved in normal embryonic implantation, trophoblast invasion, placentation, and recurrent miscarriages are characterized by defective placentation and microthrombi in the placental vasculature. Although recurrent miscarriage is a heterogeneous condition the relationship between abnormalities in the haemostatic pathways and pregnancy outcome is increasingly recognized. The challenge we face is how to discriminate between women who are destined to miscarry from those whose pregnancy will be successful. Considering the crucial role of thrombomodulin and tissue factor in coagulation and in embryonic development, we have performed a study using specific assays for thrombomodulin, tissue factor activity and procoagulant phospholipids in association with other parameters in 30 early (under 12weeks) and 32 late (over 22weeks) pregnancy loss women and compared them with 62 normal pregnancy women and 35 non-pregnant women. Plasma levels of tissue factor activity, thrombomodulin activity, and procoagulant phospholipids were significantly higher in patients than in control subjects. In addition the tissue factor activity/free tissue factor pathway inhibitor ratio was higher in patients than in controls. Interestingly, patients with late pregnancy loss had higher tissue factor activity/free tissue factor pathway inhibitor ratios than patients with early pregnancy loss. The combinations of these different parameters reveal an increase in procoagulant activity which could be secondary to endothelial damage or coagulation activation and then are involved in the pathogenesis of pregnancy loss. Their simultaneous measurement of these activities might provide a new tool to assess the prognosis of pregnancy loss.

Activation of coagulation in amniotic fluid during normal human pregnancy

INTRODUCTION

Amniotic fluid (AF) is an important medium for fetal development which exhibits high procoagulant activities; however, the role of these procoagulants during pregnancy has not been elucidated and might be associated with pregnancy complications. The current study aimed to evaluate factor X (FX) activation and its association with tissue factor (TF), tissue factor pathway inhibitor (TFPI) and coagulation activation markers in AF during normal human pregnancy.

METHODS

Activation of FX and concentration of TF, free TFPI, D-dimer and prothrombin fragments (F1+2) were evaluated in AF samples obtained for chromosome analysis from 91 women with normal pregnancy: 65 samples were taken from patients at 16-20 weeks of gestation, 9 samples were drawn at 21-30 weeks and 17 samples--after 30 weeks of gestation.

RESULTS

Activation of FX in AF significantly increased during normal pregnancy (from 65±41 to 205±80 equivalent RVV ng/mg total protein, P<0.0001). TF and TFPI levels in AF also rose with gestational age. In contrast, the AF concentration of D-dimer and F1+2, markers of coagulation activation significantly decreased when expressed per mg total protein. Levels of free TFPI correlated with TF (r=0.5, P<0.001), and were 8-fold higher than those of TF during pregnancy.

CONCLUSION

High levels of TFPI might be associated with the inhibition of procoagulant activity in amniotic fluid during normal pregnancy, which may account for the rarity of clinical amniotic fluid embolism.

Evidence of maternal platelet activation, excessive thrombin generation, and high amniotic fluid tissue factor immunoreactivity and functional activity in patients with fetal death

OBJECTIVE

Fetal death can lead to disseminated intravascular coagulation or fetal death syndrome. However, currently it is not clear what are the changes in the coagulation system in patients with a fetal death without the fetal death syndrome. This study was undertaken to determine: (1) whether fetal death in the absence of fetal death syndrome is associated with changes in hemostatic markers in maternal plasma and amniotic fluid; and (2) whether maternal hypertension or placental abruption are associated with further changes in the hemostatic profile of these patients.

METHODS

A cross-sectional study included the following: (1) determination of changes in markers of coagulation and platelet activation in patients with a normal pregnancy (n = 71) and patients with fetal demise (FD) without disseminated intravascular coagulation (n = 65); (2) determination of the amniotic fluid (AF)-tissue factor concentration and activity, as well as the concentrations of thrombin-antithrombin III (TAT) complexes in patients with a normal pregnancy (n = 25) and those with a FD (n = 36) who underwent amniocentesis. Plasma and AF concentrations of TAT complexes and TF (an index of thrombin generation), as well as maternal plasma concentrations of sCD40L (a marker of platelet activation), tissue factor pathway inhibitor (TFPI) and prothrombin fragments (PF) 1 + 2 (also an indicator of in vivo thrombin generation) were measured by ELISA. TF and TFPI activity were measured using chromogenic assays.

RESULTS

(1) patients with FD without hypertension had a higher median maternal plasma sCD40L concentration than normal pregnant women (P < 0.001); (2) patients with FD had a higher median maternal plasma TAT III complexes than women with a normal pregnancy (P < 0.001); (3) the median AF-TF concentration and activity were higher in the FD group than in the normal pregnancy group (P < 0.001 for both); (4) patients with preeclampsia and FD had a higher median maternal plasma immunoreactive TF concentration than both normotensive patients with FD and women with normal pregnancies (P < 0.001 and P = 0.001, respectively); (5) the median plasma TF activity was higher in patients with preeclampsia and FD than that of women with normal pregnancies (P = 0.003); (6) among patients with a FD, those with placental abruption had a higher median AF-TAT complexes concentration than those without abruption (P = 0.0004).

CONCLUSIONS

Our findings indicate that: (1) mothers with a FD have evidence of increased in vivo thrombin generation and platelet activation than women with normal pregnancies; (2) patients with a FD and hypertension had a higher degree of TF activation than those with fetal death but without hypertension; (3) the AF of women with a FD had a higher median TF concentration and activity than that of normal pregnant women. AF can be a potential source for tissue factor and it participates in the development of fetal death syndrome in patients with a retained dead fetus.

High tissue factor activity and low tissue factor pathway inhibitor concentrations in patients with preterm labor

OBJECTIVE

Preterm labor (PTL) has been associated with an increased thrombin generation in the maternal circulation and amniotic fluid. Tissue factor (TF) is a potent initiator of the coagulation cascade, which can trigger the hemostatic system to generate thrombin. The aims of this study were to determine whether spontaneous PTL with intact membranes is associated with changes in the maternal plasma concentrations and activity of TF as well as tissue factor pathway inhibitor (TFPI).

METHODS

This cross-sectional study included women in the following groups: (1) normal pregnancies (n = 86); (2) term pregnancies in spontaneous labor (TIL) (n = 67) and not in labor (TNL) (n = 88); and (3) patients with spontaneous PTL and intact membranes (n = 136) that were classified into three sub-groups: (a) PTL without intra-amniotic infection and/or inflammation (IAI) who delivered at term (n = 49); (b) PTL without IAI who delivered preterm (n = 54); and (c) PTL with IAI who delivered preterm (n = 33). Plasma concentrations of TF and TFPI were measured by ELISA, and their activity was measured by chromogenic assays. Non-parametric statistics were used for analysis.

RESULTS

(1) Among women at term, those with spontaneous labor had a higher median maternal plasma TF and a lower median TFPI concentration than those without labor. (2) Patients with PTL had a significantly lower median maternal plasma TFPI concentration than that of normal pregnant women, regardless of the presence of IAI. (3) There was no significant difference in the median maternal plasma TF concentration between patients with a normal pregnancy and those with PTL. (4) In contrast, the median maternal plasma TF activity was higher among patients with PTL than in women with normal pregnancies, regardless of the presence of IAI or preterm delivery. (5) However, maternal plasma TFPI activity did not differ among the study groups.

CONCLUSION

Women with preterm parturition, in contrast to those in labor at term, have a higher TF activity and a lower TFPI concentration, without a significant change in the median maternal plasma TF concentration. These observations suggest that the increased thrombin generation reported in patients with PTL may be the result of activation of the extrinsic pathway of the coagulation cascade. In addition, the increased thrombin generation reported in patients with PTL could be due to insufficient anti-coagulation, as reflected by the low maternal plasma TFPI concentration.

Changes in amniotic fluid concentration of thrombin-antithrombin III complexes in patients with preterm labor: evidence of an increased thrombin generation

OBJECTIVE

Preterm labor is associated with excessive maternal thrombin generation, as evidenced by increased circulating thrombin-antithrombin (TAT) III complexes concentration. In addition to its hemostatic functions, thrombin has uterotonic properties that may participate in the mechanism leading to preterm birth in cases of intrauterine bleeding. Thrombin also has a proinflammatory role, and inflammation is associated with increased thrombin generation. The aim of this study was to determine whether intra-amniotic infection/inflammation (IAI) is associated with increased amniotic fluid (AF) thrombin generation in women with preterm and term deliveries.

STUDY DESIGN

This cross-sectional study included the following groups: (1) mid-trimester (n = 74); (2) term not in labor (n = 39); (3) term in labor (n = 25); (4) term in labor with IAI (n = 22); (5) spontaneous preterm labor (PTL) who delivered at term (n = 62); (6) PTL without IAI who delivered preterm (n = 59); (7) PTL with IAI (n = 71). The AF TAT III complexes concentration was measured by enzyme linked immunosorbent assay (ELISA). Non-parametric statistics were used for analysis.

RESULTS

(1) TAT III complexes were identified in all AF samples; (2) patients with PTL who delivered preterm, with and without IAI, had a higher median AF TAT III complexes concentration than those with an episode of PTL who delivered at term (p < 0.001, p = 0.03, respectively); (3) among patients with PTL without IAI, elevated AF TAT III complexes concentration were independently associated with a shorter amniocentesis-to-delivery interval (hazard ratio, 1.5; 95% CI, 1.07-2.1); (4) among patients at term, those with IAI had a higher median AF TAT III complexes concentration than those without IAI, whether in labor or not in labor (p = 0.02); (5) there was no significant difference between the median AF TAT III complexes concentration of patients at term with and without labor; (6) patients who had a mid-trimester amniocentesis had a lower median AF TAT III complexes concentration than that of patients at term not in labor (p < 0.001).

CONCLUSIONS

We present herein a distinct difference in the pattern of intra-amniotic thrombin generation between term and preterm parturition. PTL leading to preterm delivery is associated with an increased intra-amniotic thrombin generation regardless of the presence of IAI. In contrast, term delivery is associated with an increased intra-amniotic thrombin generation only in patients with IAI.

Amniotic fluid embolism: an evidence-based review

We conducted an evidence-based review of information about [corrected] amniotic fluid embolism (AFE). The estimated incidence of AFE is 1:15,200 and 1:53,800 deliveries in North America and Europe, respectively. The case fatality rate and perinatal mortality associated with AFE are 13-30% and 9-44%, respectively. Risk factors associated with an [corrected] increased risk of AFE include advanced maternal age, placental abnormalities, operative deliveries, eclampsia, polyhydramnios, cervical lacerations, [corrected] and uterine rupture. The hemodynamic response in [corrected] AFE is biphasic, with initial pulmonary hypertension and right ventricular failure, followed by left ventricular failure. Promising therapies include selective pulmonary vasodilators and recombinant activated factor VIIa. Important topics for future research are presented.

A link between a hemostatic disorder and preterm PROM: a role for tissue factor and tissue factor pathway inhibitor

OBJECTIVE

Vaginal bleeding is a risk factor for preterm PROM (PPROM). A disorder of decidual hemostasis has been implicated in the genesis of PROM. Indeed, excessive thrombin generation has been demonstrated in PPROM both before and at the time of diagnosis. Decidua is a potent source of tissue factor (TF), the most powerful natural pro-coagulant. A decidual hemostatic disorder may link vaginal bleeding, PPROM and placental abruption. This study was conducted to determine the behaviour of maternal TF and its natural inhibitor, the tissue factor pathway inhibitor (TFPI) in PPROM.

METHODS

This cross-sectional study included women with PPROM (n = 123) and women with normal pregnancies (n = 86). Plasma concentrations of TF and TFPI were measured by a sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) The median maternal plasma TF concentration was significantly higher in patients with PPROM than in women with normal pregnancies (median: 369.5 pg/mL; range: 3.27-2551 pg/mL vs. median: 291.5 pg/mL; range: 6.3-2662.2 pg/mL respectively, p = 0.001); (2) the median maternal TFPI plasma concentration was significantly lower in patients with PPROM than in women with normal pregnancies (median: 58.7 ng/mL; range: 26.3-116 ng/mL vs. median: 66.1 ng/mL; range: 14.3-86.5 ng/mL respectively, p = 0.019); (3) there was no correlation between the plasma concentration of TF and TFPI and the gestational age at sample collection; and (4) among patients with PPROM there was no association between the presence of intra-amniotic infection or inflammation and median plasma concentrations of TF and TFPI.

CONCLUSIONS

(1) Patients with PPROM have a higher median plasma concentration of TF and a lower median plasma concentration of TFPI than women with normal pregnancies. (2) These findings suggest that PPROM is associated with specific changes in the hemostatic/coagulation system.

Procoagulants and anticoagulants in fetal blood. A literature survey

In intrauterine life, hemostasis is maintained by the same components as in extrauterine life (blood platelets, coagulation and fibrinolysis systems, involvement of the vascular wall); in the fetus, however, these components show significant differences of a quantitative/qualitative nature. In the present study, we surveyed the literature on the coagulation system in the fetus. We focused on the velocity of development of the coagulation system, being reflected in the increased concentration of all procoagulants and anticoagulants (a rise from approximately 20% in the middle of pregnancy to about 60% or more in the period of labor; exceptions: factors V, VIII and XIII which in the labor period reach the adult level) and screening test results (prothrombin time, aPTT - activated prothrombin time, and thrombin time). Reference values were given for the 19-38 weeks of pregnancy and the labor term. Biochemical features of fetal fibrinogen and PIVKA factors were also discussed. The role of activated protein C (APC) in the maintenance of balance between procoagulants and anticoagulants was postulated as well as the role of APC in the formation of thrombin activatable fibrinolysis inhibitor (TAFI).

Tissue factor and its natural inhibitor in pre-eclampsia and SGA

OBJECTIVE

Tissue factor (TF), the major activator of the extrinsic pathway of coagulation, is abundant in the placenta and decidua. The aim of this study was to determine the maternal plasma concentrations of TF and its primary inhibitor, tissue factor pathway inhibitor (TFPI), in women who delivered small for gestational age (SGA) neonates, and in pre-eclampsia.

STUDY DESIGN

A cross-sectional study included the following groups: 1) women with normal pregnancies (n = 86); 2) patients who delivered SGA neonates (n = 61) and 3) women with pre-eclampsia (n = 133). Maternal plasma concentrations of TF and TFPI were measured by a sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

1) Women with pre-eclampsia had a significantly higher median plasma concentration of TF than patients with a normal pregnancy (median: 1187 pg/mL; range: 69-11675 vs. median: 291.5 pg/mL; range: 6.3-2662.2; p < 0.0001, respectively); 2) Similarly, TFPI concentrations were higher in pre-eclampsia than in normal pregnancy (median: 87.5 ng/mL; range 25.4-165.1 vs. median: 66.1 ng/mL; range: 14.3-86.5; p < 0.0001, respectively); 3) Surprisingly, mothers with SGA neonates had a lower median maternal plasma concentration of TF (median: 112.2 pg/mL; range: 25.6-1225.3) than women with a normal pregnancy (p < 0.0001).

CONCLUSION

1) Maternal plasma concentrations of TF in patients with pre-eclampsia, but not in those who delivered an SGA neonate, were higher than in women with normal pregnancies; 2) Although the role of immunoreactive plasma TF in coagulation remains controversial, our observations suggest that changes are present in the context of complications of pregnancy.

Tissue factor-dependent blood coagulation is enhanced following delivery irrespective of the mode of delivery

BACKGROUND

The risk of thrombosis is clearly increased in the postpartum period. Mice with a targeted deletion of the transmembrane domain of tissue factor (TF) develop serious activation of blood coagulation and widespread thrombosis after delivery.

OBJECTIVE AND METHODS

We hypothesized that TF, abundantly present in placental tissue, is released during delivery, resulting in the activation of blood coagulation. We measured sensitive markers for TF-dependent activation of coagulation before and after induction of labor in two groups: a vaginal delivery (VAG) group and a cesarean section (CS) group.

RESULTS

One hour after delivery, soluble TF (sTF) significantly increased in both groups [VAG group (mean +/- SD) 226 +/- 42 to 380 +/- 42 pg mL(-1) and CS group 193 +/- 17 to 355 +/- 44 pg mL(-1)]. The day after delivery, sTF was somewhat less increased. Both groups also showed an increase in factor VIIa, indicating activation of the TF pathway of coagulation. Indeed, after delivery, TF-dependent coagulation, as measured by the TF clotting time assay, was significantly enhanced. Increased plasma levels of prothrombin fragment 1 + 2 and thrombin-antithrombin complexes demonstrated thrombin generation following delivery. TF pathway-dependent activation of coagulation upon delivery was not blocked by TF pathway inhibitor and was not dependent on the mode of delivery.

CONCLUSION

The postdelivery increase in TF-dependent activation of coagulation is likely to be a natural mechanism to prevent excessive blood loss during and after delivery, and may also indicate a novel mechanism by which puerperal women have an increased risk of venous thromboembolism.

Changes in haemostasis during normal pregnancy: does homocysteine play a role in maintaining homeostasis?

Homocysteine, derived from the demethylation of the ammo acid methionine, is either further catabolised by trans-sulfuration to cysteine or remethylated to methionine. Remethylation to methionine requires the cofactors, folate and vitamin B12. Folate is an effective homocysteine-lowering agent and, thus, homocysteine and folate status are inversely related. Hyperhomocysteinaemia is a strong independent risk factor for venous thromboembolism (VTE) and is associated with adverse pregnancy outcomes such as pre-eclampsia, placental abruption, early pregnancy loss and neural-tube defects. Pregnancy is a risk factor for VTE as a result of prothrombotic changes in levels of haemostatic factors. However, despite this hypercoagulable state, the incidence of pregnancy-associated VTE is relatively low. Hyperhomocysteinaemia is associated with abnormalities in markers of coagulation activation, and recent research suggests that folic acid supplementation, as well as lowering homocysteine, lowers markers of coagulation activation and increases levels of coagulation inhibitors. Tissue factor (TF) is the initiator of blood coagulationin vivo, and homocysteine induces TF expressionin vitro. During pregnancy, monocyte TF expression is lower than that in the non-pregnant state, and this lowering of TF may act to counterbalance increases in coagulation activation. Furthermore, despite a high folate requirement, several studies have reported that homocysteine is lower in normal pregnancy than in the non-pregnant state. Although the exact mechanism of homocysteine lowering during pregnancy is unclear, one possible outcome of lower homocysteine may be the protection of women from pregnancy complications and VTE, and thus lower homocysteine may contribute to maintaining homeostasis in haemostasis.

Protein C, protein S, and thrombomodulin in amniotic fluid. A preliminary study

OBJECTIVES

The main components of protein C anticoagulant system are protein C (PC), protein S (PS) and thrombomodulin (TM); the system plays a protective role in pregnancy, mainly because it prevents the utero-placental circulation from local thrombosis. It is unknown whether the protein C anticoagulant pathway exists in amniotic fluid. The aim of the present study is to find out whether these three components are present in amniotic fluid.

STUDY DESIGN

The study group consisted of 50 parturients with an uneventful pregnancy and birth and 25 non-pregnant controls. Amniotic fluid and blood were sampled at the end of the 1st stage of labor. PC, PS and TM were measured by immunoenzymatic method.

RESULTS

All the samples of amniotic fluid contained measurable amounts of antigens of PC, PS and TM, although their concentrations were significantly lower than in the mother's blood: (i) The concentration of PC in amniotic fluid was 6.24+/-3.50% and PS 2.40+/-1.64%, while in the mothers' plasma it was 138.26+/-12.38% and 93.15+/-13.24%, respectively (P<0.0001). (ii) TM concentration in amniotic fluid constituted 63.92% of the concentration in the mother's blood (2.71+/-1.21 ng/mL vs. 4.24+/-0.88 ng/mL, P<0.001).

CONCLUSION

Protein C, protein S and thrombomodulin are physiological constituents of the amniotic fluid. As their concentrations are low, it is reasonable to assume that they cannot counterbalance the procoagulant activity of amniotic fluid.

Thrombin activatable fibrinolysis inhibitor (TAFI) in human amniotic fluid. A preliminary study

Thrombin activatable fibrinolysis inhibitor (TAFI) has been studied in normal and complicated pregnancies by a number of investigators, but there is no information on TAFI in amniotic fluid. In our study we asked two questions: (i) whether TAFI is present in amniotic fluid and in what concentration, (ii) whether its concentration is comparable to that in the blood. The study group consisted of 68 parturient women in the first stage of labour. 20 age-matched non-pregnant women constituted the control group. TAFI antigen was measured by immunoenzymatic method (ELISA) and TAFI activity with Actichrome Plasma TAFI Activity Kit by American Diagnostica. The concentration of TAFI antigen in amniotic fluid was 53.25 ng/ml (median) (range: 44.58-76.20 ng/ml) and in mothers' plasma it was 55.46 ng/ml (median) (range: 39.77-68.54 ng/ml); the difference was not statistically significant (p>0.3388). TAFI activity in amniotic fluid was relatively low (median: 3.00 microg/ml, range 0.50-5.45 microg/ml), while the activity in the mothers' plasma was more than three times higher (median 10.50 microg/ml; range: 7.60-13.50 microg/ml) (p<0.0004). TAFI antigen and TAFI activity in plasma of non-pregnant women were as high as in plasma of delivering women. We have concluded that TAFI is a physiological constituent of amniotic fluid. It is possible that TAFI is partially accountable for the antifibrinolytic potential of amniotic fluid.

A hypothesis regarding complement activation and amniotic fluid embolism

Amniotic fluid embolism, a rare, sudden and often fatal illness of pregnancy may not be a true embolic event resulting from the physical obstruction of the pulmonary vasculature. The high degree of variability in symptoms, the lack of characteristic findings on radiological exam, the absence of a dose-response effect on symptoms, and the occasional occurrence of coagulopathies are not entirely consistent with a physical block to the circulation as the main mechanism of disease. Alternatively, it might be the result of complement activation initiated by fetal antigen leaking into the maternal circulation. This rare immune response may be initiated by a rare pathological antigen, or by common antigens presented uncommonly--in amount, timing, or frequency of entry into the maternal circulation. Some very early evidence in AFE patients supports this hypothesis but is not conclusive. Complement levels remain well within the normal range during uncomplicated parturition. A prior theory that AFE might be a result of maternal anaphylaxis to fetal antigen has much less evidence to support it. The disseminated intravascular coagulation often seen in this and other serious obstetrical illnesses may be a secondary result of complement activation rather than the direct introduction of pro-coagulants into the maternal circulation although the link between the complement and coagulation pathways, if any, remains poorly defined. Through currently available laboratory testing, both the complement hypothesis and the anaphylaxis mechanism are able to be assessed. Direct measurement of serum complement as well as serum tryptase and urinary histamine are readily obtained tests in community hospitals as well as tertiary care hospitals. If the hypothesis proves true, this investigation may be of profound importance to understanding immune tolerance. Rather, than asking why one pregnant woman in 20,000 develops a violent immune reaction to the fetus, a better question is why do not all pregnant women reject the fetus which is a large collection of foreign antigens?

Immunologic quantitation of tissue factors

The large number of conflicting reports on the presence and concentration of circulating tissue factor (TF) in blood generates uncertainties regarding its relevance to hemostasis and association with specific diseases. We believe that the source of these controversies lies in part in the assays used for TF quantitation. We have developed a highly sensitive and specific double monoclonal antibody fluorescence-based immunoassay and integrated it into the Luminex Multi-Analyte Platform. This assay, which uses physiologically relevant standard and appropriate specificity controls, measures TF antigen in recombinant products and natural sources including placenta, plasma, cell lysates and cell membranes. Comparisons of reactivity patterns of various full-length and truncated TFs on an equimolar basis revealed quantitative differences in the immune recognition of TFs by our antibodies in the order of TF 1-263 > 1-242 > 1-218 > placental TF. Despite this differential recognition, all TF species are quantifiable at concentrations < or = 2 pM. Using a calibration curve constructed with recombinant TF 1-263 and plasma from healthy individuals (n = 91), we observed the concentration of TF antigen in plasma to be substantially lower than that generally reported in the literature: TF antigen in plasma of 72 individuals (79%) was below 2 pM (quantitative limit of our assay); TF antigen levels between 2.0 and 5.0 pM could be detected in six individuals (7%); and in 14% (13 plasmas), the non-specific signal was higher than the specific signal, and thus TF levels could not be determined. These differential recognition patterns affect TF quantitation in plasma and should be considered when evaluating plasma TF-like antigen concentrations.

Tissue factor and tissue factor pathway inhibitor: a potential role in pregnancy and obstetric vascular complications?

Tissue factor (TF) is the principal cellular initiator of normal blood coagulation. As a result it is considered to be a major regulator of haemostasis and thrombogenesis. In vivo TF activity is regulated by specific circulating inhibitor known as "tissue factor pathway inhibitor (TFPI)". TF is also essential for other cellular processes including embryogenesis and angiogenesis as well as in implantation where it is particularly important in the first trimester. TF is highly expressed in syncytiotrophoblasts (STB) while TFPI is expressed in human umbilical vein endothelial cells (HUVEC). TFPI may be internalized via an endocytic pathway and recycled to the cell surface. The procoagulant tendency of STB may reflect a physiological need for immediate inhibition of hemorrhage in the placental intervillous spaces. Furthermore, the haemostatic balance involving STB and HUVEC may be critical for normal placental function and pregnancy outcome. Homozygous knockouts of both TF and TFPI are generally lethal in fetal mice; heterozygotes survive but with altered coagulation parameters. Despite their apparent association with placental microcirculation-thrombi-formation only few studies have addressed the role of TF and TFPI in the pathogenesis of gestational vascular complications. In this context, detailed studies could provide clinically relevant information.

[Amniotic fluid embolism: a review]

Amniotic fluid embolism occurs rarely but is a leading cause of maternal mortality. It is a difficult and somewhat intangible diagnosis that warrants a high index of suspicion by physicians. AFE is an unpredictable, unpreventable, and, for the most part, an untreatable obstetric emergency. Management of this condition includes prompt recognition of the signs and symptoms, aggressive resuscitation efforts, and supportive therapy. Any delays in diagnosis and treatment can result in increased maternal and/or foetal impairment or death. Whereas once the invariable outcome of AFE was death of the mother, today the prognosis is somewhat brighter thanks to increased awareness of the syndrome and advances in intensive care medicine. No laboratory test is specific to attest the diagnosis and autopsy must to be realised in case of maternal death. Although non-specific, the diagnosis of AFE could be supported by the observation of amniotic fluid in the central venous blood as well as in the bronchoalveolar fluid. This easy and quick test will be helpful in decision-making. Prompt and aggressive supportive treatment is required to lessen an otherwise dismal outcome, which may include death and permanent disability. This article provides an account of the protean clinical features, pathogenesis, and principles involved in treatment.

Amniotic fluid embolism

INCIDENCE

Amniotic fluid embolism is a catastrophic syndrome that occurs during pregnancy or in the immediate postpartum period. Multiple case reports have described the clinical findings and have reported variable success with supportive care. There has been discrepancy with respect to the incidence and mortality of amniotic fluid embolism. One likely explanation for this inconsistency is the lack of sensitive and specific diagnostic studies to definitively identify cases of amniotic fluid embolism, leading to both over- and underreporting. Despite the variation in reported incidence and mortality, amniotic fluid embolism remains a life-threatening condition with significant morbidity and mortality for the pregnant woman. It is the fifth most common cause of maternal mortality in the world.

DIAGNOSIS

The diagnosis of amniotic fluid embolism continues to be a clinical diagnosis and a diagnosis of exclusion based on the rapid development of a complex constellation of findings with sudden cardiovascular collapse, acute left ventricular failure with pulmonary edema, disseminated intravascular coagulation, and neurologic impairment. Given the significant morbidity and mortality associated with this condition, a high index of suspicion is warranted. Suspected risk factors have included tumultuous labor, trauma, multiparity, increased gestational age, and increased maternal age. However, many patients who develop amniotic fluid embolism have no obvious risk factors.

MANAGEMENT

Patients with amniotic fluid embolus are best managed using a multidisciplinary approach. There are no pharmacologic or other therapies that prevent or treat the amniotic fluid embolism syndrome, and supportive care typically involves aggressive treatment of multiple types of shock simultaneously. In this article we discuss the clinical presentation of amniotic fluid embolism syndrome as well as current opinions regarding pathophysiology, diagnosis, and management.

Effect of amniotic fluid on coagulation and platelet function in pregnancy: an evaluation using thromboelastography

Amniotic fluid embolism is a rare obstetric complication. The exact pathogenesis of this syndrome remains unknown and significant controversy exists whether coagulopathy should always be present. We used thromboelastography to assess the effect of amniotic fluid on coagulation and platelet function in pregnant women. Different volumes of amniotic fluid (10-60 microl) were added to blood (330 microl) from pregnant women and thromboelastography variables determined. There were three important findings. R time, reflecting time to first clot formation, was significantly decreased with the addition of 10 microl amniotic fluid; platelet function, as determined by Reopro-TEG technique, was increased with the addition of 30 microl of amniotic fluid; and there was no evidence of fibrinolysis in any samples studied. In conclusion, our study substantiates the hypothesis that coagulation profile changes are invariable accompaniments of amniotic fluid embolism.

Haemostasis in normal pregnancy: a balancing act?

Pregnancy is a risk factor for venous thrombosis and the incidence of venous thromboembolism during normal pregnancy is 6-fold higher during pregnancy than in the general female population of child-bearing age. This incidence is, however, remarkably low given the increases in markers of haemostatic activation observed during normal pregnancy. During normal healthy pregnancy there are substantial changes in the haemostatic system, many of which are procoagulant and supposed to be in preparation for the haemostatic challenge of delivery. Normal haemostasis requires a balance between coagulation and fibrinolysis to maintain the integrity of the vasculature, and complex physiological changes are evident during pregnancy which appear to ensure a constant coagulation/fibrinolysis balance. This balance is maintained, at least partly, by an increase in fibrinolytic activity, but decreases in other factors such as factor XI and monocyte tissue factor expression may also serve to counterbalance procoagulant changes.

Amniotic fluid: not just fetal urine anymore

Amniotic fluid (AF) is a complex substance essential to fetal well-being. This article reviews recent discoveries and the current understanding of the origin and circulation of AF and its nutritive, protective, and diagnostic functions. Future directions for AF research are also discussed.

Amniotic fluid embolus: can we affect the outcome?

PURPOSE OF REVIEW

Amniotic fluid embolism is a rare catastrophe unique to pregnancy. Its mortality rate remains high despite efforts at prompt and aggressive management protocols, highlighting the need to maintain a high index of suspicion.

RECENT FINDINGS

The intrusion of amniotic fluid into the maternal bloodstream may lead in certain women to a complex series of physiological reactions mimicking those seen in human anaphylaxis or sepsis, negating the purely embolic phenomenon theory as previously understood. The clinical picture is the sudden onset of cardiovascular collapse, cyanosis, haemorrhage or disseminated intravascular coagulopathy, during or soon after delivery.

SUMMARY

The mainstay of a successful outcome remains the identification of high-risk patients, as well as early clinical diagnosis and management.

Tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in the placenta and myometrium

BACKGROUND

Placental abruption is mainly due to the rupture of the uterine spiral arteries, but adjacent tissues are also damaged and substances derived from disintegrated placenta and myometrium probably cause coagulation disturbances, such as hypofibrinogenemia and disseminated intravascular coagulation (DIC).

AIM

To measure whether placenta and myometrium are significant sources of tissue factor (TF) and tissue factor pathway inhibitor (TFPI), the components of key role in the initiation of coagulation.

MATERIALS AND METHODS

Strips of placenta and myometrium were obtained from 48 women delivered by cesarean section at term. TF and TFPI concentrations were measured by immunoenzymatic method (ELISA) in tissue homogenates.

MAIN RESULTS

Concentration of TF in placenta and myometrium was 31 (25-37) and 7.4 (4.9-11.4) ng/mg of total protein, respectively. In the plasma of the same women, it was 0.004ng/mg of total protein. TFPI concentration was 13 (10-17) ng/mg of total protein in placenta, 4.5 (3.1-7.3) ng/mg in myometrium, and 0.70 (0.50-0.80) ng/mg in blood plasma protein.

CONCLUSION

The levels of TF in placenta and myometrium, over TF in blood plasma may be clinically significant in obstetrics, for instance, in the etiology of DIC in placental abruption. The concentration of TFPI-natural inhibitor of TF-seems to be too low to prevent initiation of coagulation.