Cost-effectiveness of screening for the factor V Leiden mutation in pregnant women

Venous Thromboembolism in Pregnancy: A Review of Diagnosis, Management, and Prevention

Venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism, is a leading cause of maternal morbidity and mortality worldwide. Physiological changes that occur in a normal pregnancy increase the risk for VTE by 4-5-fold in the antepartum period and 30-60-fold in the immediate postpartum period. Compressive ultrasonography is the diagnostic test of choice for deep vein thrombosis. Both ventilation/perfusion scanning and computed tomography pulmonary angiography can reliably diagnose pulmonary embolism. Anticoagulation for a minimum of 3 months, typically with low molecular weight heparin, is the treatment of choice for pregnancy-associated VTE (PA-VTE). Despite the significant societal burden and potentially devastating consequences, there is a paucity of data surrounding the prevention of PA-VTE, resulting in major variations between international guidelines. This review will summarize the current recommendations for diagnosis, management, and prevention of PA-VTE.

Pearls in clinical obstetrics: challenges in anticoagulation in pregnancy

Women are at increased risk for venous thromboembolism (VTE) during both pregnancy and in the post-partum period. We have conducted a comprehensive literature review of the use of anticoagulation in pregnancy for pregnant women at increased risk for VTE. Multiple factors, including physiologic and pharmacokinetic changes make the treatment and prevention of VTE complicated in pregnancy. Adequate treatment and prevention of VTE in pregnancy is critically important, yet good quality medical studies continue to be lacking. There is a growing amount of data for the use of low molecular weight heparin (LMWH) in pregnant women and this remains the treatment of choice in most indications. For both prophylactic and therapeutic treatments, when LMWHs are chosen, monitoring of antifactor Xa level, although controversial, is advised. Women with prosthetic valve who become pregnant face challenges in regard of type of anticoagulation, dosing and monitoring during pregnancy. Delivery options and peripartum care should be defined with a multidisciplinary approach and taking patient's preference and autonomy in consideration. More high-quality research on this topic is needed to guide the clinical care of this unique population.

A systematic review of cost-effectiveness analysis of screening interventions for assessing the risk of venous thromboembolism in women considering combined oral contraceptives

Use of combined oral contraceptives (COCs) by women increases the risk of venous thromboembolism (VTE), which can have a major impact on an individuals' quality of life. VTE is also associated with an increase in healthcare costs. Our aim was to systematically review cost-effectiveness analyses (CEAs) considering any screening for risk of VTE in women using COCs. The quality of reporting in each study was assessed, a summary of results was prepared, and the key drivers of cost effectiveness in each of the eligible CEAs were identified. A search strategy using MeSH terms was performed in MEDLINE, Embase, the Centre for Review and Dissemination (CRD) database including the Economic Evaluation Database from the UK National Health Service, and Cochrane reviews. Two reviewers independently screened and determined the final articles, and a third reviewer resolved any discrepancies. Consolidated Health Economic Evaluation Reporting Standards was used to assess the quality of reporting in terms of perspective, effectiveness measures, model structure, cost, time-horizon and discounting. Four publications (three from Europe, one from the United States) were eligible for inclusion in the review. According to current criteria, relevant elements were sometimes not captured and the sources of epidemiological and effectiveness data used in the CEAs were of limited quality. The studies varied in terms of type of costs assessed, country settings, model assumptions and uncertainty around input parameters. Key drivers of CEAs were sensitivity and specificity of the test, incidence rate of VTE, relative risk of prophylaxis, and costs of the test. The reviewed studies were too dissimilar to draw a firm conclusion on cost-effectiveness analysis about universal and selective screening in high-risk groups. The new emerging diagnostic tools for identifying women at risk of developing VTE, that are more predictive and less costly, highlight the need for more studies that apply the latest evidence and utilize robust methods for cost-effectiveness analysis. This information is required to improve decision making for this pertinent issue within personalized medicine.

Hereditary risk factors for thrombophilia and probability of venous thromboembolism during pregnancy and the puerperium

Venous thromboembolism (VTE) is a leading cause of maternal mortality. Few studies have evaluated the individual risk of gestational VTE associated with heritable thrombophilia, and current recommendations for antenatal thromboprophylaxis in women with severe thrombophilia such as homozygous factor V Leiden mutation (FVL) depend on a positive family history of VTE. To better stratify thromboprophylaxis in pregnancy, we aimed to estimate the individual probability (absolute risk) of gestational VTE associated with thrombophilia and to see whether these risk factors are independent of a family history of VTE in first-degree relatives. We studied 243 women with the first VTE during pregnancy and the puerperium and 243 age-matched normal women. Baseline incidence of VTE of 1:483 pregnancies in women ≥35 years and 1:741 deliveries in women <35 years was assumed, according to a recent population-based study. In women ≥35 years (<35 years), the individual probability of gestational VTE was as follows: 0.7% (0.5%) for heterozygous FVL; 3.4% (2.2%) for homozygous FVL; 0.6% (0.4%) for heterozygous prothrombin G20210A; 8.2% (5.5%) for compound heterozygotes for FVL and prothrombin G20210A; 9.0% (6.1%) for antithrombin deficiency; 1.1% (0.7%) for protein C deficiency; and 1.0% (0.7%) for protein S deficiency. These results were independent of a positive family history of VTE. We provide evidence that unselected women with these thrombophilias have an increased risk of gestational VTE independent of a positive family history of VTE. In contrast to current guidelines, these data suggest that women with high-risk thrombophilia should be considered for antenatal thromboprophylaxis regardless of family history of VTE.

Genetic screening for the predisposition to venous thromboembolism: a cost-utility analysis of clinical practice in the Italian health care system

OBJECTIVES

In the Italian health care system, genetic tests for factor V Leiden and factor II are routinely prescribed to assess the predisposition to venous thromboembolism (VTE) of women who request oral contraception. With specific reference to two subpopulations of women already at risk (i.e., familial history or previous event of VTE), the study aimed to assess whether current screening practices in Italy are cost-effective.

METHODS

Two decisional models accrued costs and quality-adjusted life-years (QALY) annually from the perspective of the National Health Service. The two models were derived from a decision analysis exercise concerning testing practices and consequent prescribing behavior for oral contraception conducted with 250 Italian gynecologists. Health care costs were compiled on the basis of 10-year hospital discharge records and the activities of a thrombosis center. Whenever possible, input data were based on the Italian context; otherwise, the data were taken from the international literature.

RESULTS

Current testing practices on women with a familial history of VTE generate an incremental cost-effectiveness ratio of €72,412/QALY, which is well above the acceptable threshold of cost-effectiveness of €40,000 to €50,000/QALY. In the case of women with a previous event of VTE, the most frequently used testing strategy is cost-ineffective and leads to an overall loss of QALY.

CONCLUSIONS

This study represents the first attempt to conduct a cost-utility analysis of genetic screening practices for the predisposition to VTE in the Italian setting. The results indicate that there is an urgent need to better monitor the indications for which tests for factor V Leiden and factor II are prescribed.

Testing for inherited thrombophilia and consequences for antithrombotic prophylaxis in patients with venous thromboembolism and their relatives. A review of the Guidelines from Scientific Societies and Working Groups

The clinical penetrance of venous thromboembolism (VTE) susceptibility genes is variable, being lower in heterozygous carriers of factor V Leiden and prothrombin 20210A (mild thrombophilia), and higher in the rare carriers of deficiencies of antithrombin, protein C or S, and those with multiple or homozygous abnormalities (high-risk thrombophilia). The absolute risk of VTE is low, and the utility of laboratory investigation for inherited thrombophilia in patients with VTE and their asymptomatic relatives has been largely debated, leading to the production of several Guidelines from Scientific Societies and Working Groups. The risk for VTE largely depends on the family history of VTE. Therefore, indiscriminate search for carriers is of no utility, and targeted screening is potentially more fruitful. In patients with VTE inherited thrombophilia is not scored as a determinant of recurrence, playing a minor role in the decision of prolonging anticoagulation; indeed, a few guidelines consider testing worthwhile to identify carriers of high-risk thrombophilia, particularly those with a family history of VTE. The identification of the asymptomatic carrier relatives of the probands with VTE and thrombophilia could reduce cases of provoked VTE, offering them primary antithrombotic prophylaxis during risk situations. In most guidelines, this is considered justified only for relatives of probands with a deficiency of natural anticoagulants or multiple abnormalities. Counselling the asymptomatic female relatives of individuals with VTE and/or thrombophilia before pregnancy or the prescription of hormonal treatments should be administered with consideration of the risk driven by the type of thrombophilia and the family history of VTE.

Genetic testing in the European Union: does economic evaluation matter?

OBJECTIVE

We review the published economic evaluation studies applied to genetic technologies in the EU to know the main diseases addressed by these studies, the ways the studies were conducted and to assess the efficiency of these new technologies. The final aim of this review was to understand the possibilities of the economic evaluations performed up to date as a tool to contribute to decision making in this area.

METHODS

We have reviewed a set of articles found in several databases until March 2010. Literature searches were made in the following databases: PubMed; Euronheed; Centre for Reviews and Dissemination of the University of York-Health Technology Assessment, Database of Abstracts of Reviews of Effects, NHS Economic Evaluation Database; and Scopus. The algorithm was "(screening or diagnosis) and genetic and (cost or economic) and (country EU27)". We included studies if they met the following criteria: (1) a genetic technology was analysed; (2) human DNA must be tested for; (3) the analysis was a real economic evaluation or a cost study, and (4) the articles had to be related to any EU Member State.

RESULTS

We initially found 3,559 papers on genetic testing but only 92 articles of economic analysis referred to a wide range of genetic diseases matched the inclusion criteria. The most studied diseases were as follows: cystic fibrosis (12), breast and ovarian cancer (8), hereditary hemochromatosis (6), Down's syndrome (7), colorectal cancer (5), familial hypercholesterolaemia (5), prostate cancer (4), and thrombophilia (4). Genetic tests were mostly used for screening purposes, and cost-effectiveness analysis is the most common type of economic study. The analysed gene technologies are deemed to be efficient for some specific population groups and screening algorithms according to the values of their cost-effectiveness ratios that were below the commonly accepted threshold of 30,000€.

CONCLUSIONS

Economic evaluation of genetic technologies matters but the number of published studies is still rather low as to be widely used for most of the decisions in different jurisdictions across the EU. Further, the decision bodies across EU27 are fragmented and the responsibilities are located at different levels of the decision process for what it is difficult to find out whether a given decision on genetic tests was somehow supported by the economic evaluation results.

Impact of smoking during pregnancy on functional coagulation testing

Compounds that are systemically absorbed during the course of cigarette smoking, and their metabolites, affect the coagulation system and cause endothelial dysfunction, dyslipidemia, and platelet activation leading to a prothrombotic state. In addition, smoking increases the activity of fibrinogen, homocysteine, and C-reactive protein. We hypothesize that smoking may affect functional coagulation testing during pregnancy. A secondary analysis of 371 women pregnant with a singleton pregnancy and enrolled in a multicenter, prospective observational study of complications of factor V Leiden mutation subsequently underwent functional coagulation testing for antithrombin III, protein C antigen and activity, and protein S antigen and activity. Smoking was assessed by self-report at time of enrollment (<14 weeks). None of the functional coagulation testing results was altered by maternal smoking during pregnancy. Smoking does not affect the aforementioned functional coagulation testing results during pregnancy.

ABO blood groups and thrombosis: a causal association, but is there value in screening?

ABO(H) antigens are expressed on red cells and on von Willebrand factor. An association between groups other than O and thrombosis exists: an effect that is predominantly mediated by von Willebrand factor. Overall, the risk of venous thrombosis associated with non-O has been estimated at 1.75-fold, with a higher risk (∼2.4-fold) in those with the least O(H) antigen (a combined group of A1A1/A1B/BB). Preliminary evidence also suggests that blood group may influence the venous thromboembolism risk associated with factor V Leiden. Overall, ABO(H) has a more modest effect on arterial disease, with a consistent effect observed in peripheral vascular disease and no influence evident with angina. A modest effect on myocardial infarction and stroke has been reported in some but not all studies. The potential mechanisms whereby blood group influences thrombosis, the limitations of current evidence and the current and future role of blood groups in identifying those at risk of arterial and venous disease is discussed.

Venous thromboembolism in pregnancy

In Western nations, venous thromboembolism (VTE) is an important cause of morbidity and the most common cause of maternal death during pregnancy and the puerperium. Pregnancy is a hypercoagulable state in which coagulation is activated and thrombolysis inhibited. This prothrombotic risk is compounded when hereditary and acquired thrombophilias and other prothrombotic risk factors are present. The risk of venous thrombotic events is increased fivefold during pregnancy and 60-fold in the first 3 months after delivery (postpartum period) compared with nonpregnant women. Many of the signs and symptoms of VTE overlap those of a normal pregnancy, which complicates the diagnosis. Patients with history of previous VTE should use graduated compression stockings throughout pregnancy and the puerperium, and should receive postpartum anticoagulant prophylaxis. The indications for antepartum anticoagulant prophylaxis are somewhat controversial. This article reviews the management of VTE during pregnancy and in the postpartum period.

Family history of venous thromboembolism and identifying factor V Leiden carriers during pregnancy

OBJECTIVE

To estimate whether there is a correlation between family history of venous thromboembolism and factor V Leiden mutation carriage in gravid women without a personal history of venous thromboembolism.

METHODS

This is a secondary analysis of a prospective observational study of the frequency of pregnancy-related thromboembolic events among carriers of the factor V Leiden mutation. Family history of venous thromboembolism in either first- or second-degree relatives was self-reported. Sensitivity, specificity, and positive and negative predictive values of family history to predict factor V Leiden mutation carrier status were calculated.

RESULTS

Women without a personal venous thromboembolism history and with available DNA were included (n=5,168). One hundred forty women (2.7% [95% confidence interval (CI) 2.3-3.2%]) were factor V Leiden mutation-positive. Four hundred twelve women (8.0% [95% CI 7.3-8.7%]) reported a family history of venous thromboembolism. Women with a positive family history were twofold more likely to be factor V Leiden mutation carriers than those with a negative family history (23 of 412 [5.6%] compared with 117 of 4,756 [2.5%], P<.001). The sensitivity, specificity, and positive predictive value of a family history of a first- or second-degree relative for identifying factor V Leiden carriers were 16.4% (95% CI 10.7-23.6%), 92.3% (95% CI 91.5-93.0%), and 5.6% (95% CI 3.6-8.3%), respectively.

CONCLUSION

Although a family history of venous thromboembolism is associated with factor V Leiden mutation in thrombosis-free gravid women, the sensitivity and positive predictive values are too low to recommend screening women for the factor V Leiden mutation based solely on a family history.

ABO(H) blood groups and vascular disease: a systematic review and meta-analysis

BACKGROUND

Associations between vascular disease and ABO(H) blood groups have a long history, but no consensus exists regarding its magnitude and significance, or whether it relates to all disorders equally. An accurate calculation of risk would allow direct assessment of whether the effects of non-O status on thrombosis risk are of the magnitude predicted by its effect on von Willebrand factor/FVIII levels.

METHODS AND RESULTS

We conducted a systematic review and meta-analysis of studies reporting associations with non-O blood groups. This gave pooled odds ratios of 1.25 [95% confidence interval (CI) 1.14-1.36] for myocardial infarction (MI), 1.03 (95% CI 0.89-1.19) for angina, 1.45 (95% CI 1.35-1.56) for peripheral vascular disease, 1.14 (95% CI 1.01-1.27) for cerebral ischemia of arterial origin, and 1.79 (95% CI 1.56 to 2.05) for venous thromboembolism (VTE). However, restriction to prospective MI studies only did not confirm the association (OR 1.01; 95% CI 0.84-1.23), although these studies may have failed to capture early-onset disease. For VTE, using a combined group of OO/A(2)A(2)/A(2)O as index, the combination of A(1)A(1)/A(1)B/BB gave an OR of 2.44 (95% CI 1.79-3.33) and A(1)O/ BO/A(2)B an OR of 2.11 (95% CI 1.66-2.68).

CONCLUSIONS

This study confirms the historical impression of linkage between some vascular disorders and non-O blood group status. Although the odds ratios are similar to those predicted by the effect of ABO(H) on von Willebrand factor levels, further work is required to assess risk prospectively and to refine the effect of reducing O(H) antigen expression on thrombosis. However, as non-O and particularly A(1)A(1), A(1)B, BB constitute a significant proportion of the population attributable fraction of VTE, there may be a role for more widespread adoption of ABO(H) typing in testing strategies.

Is screening for thrombophilia cost-effective?

PURPOSE OF REVIEW

The aim of this review was to examine the current evidence on the cost-effectiveness of screening for thrombophilia.

RECENT FINDINGS

Few studies have attempted to evaluate the cost-effectiveness of screening for thrombophilia. The direct medical costs associated with screening, in order to detect one case of thrombophilia and indeed to prevent a subsequent venous thromboembolism, are high. Irrespective of patient groups, selective history-based thrombophilia screening has been shown to be more cost-effective than universal or unselected population screening. When comparing across the high-risk patient groups, screening women prior to prescribing combined oral contraceptives was the least cost-effective strategy.

SUMMARY

Although thrombophilia is associated with a substantial increase in relative risk of venous thromboembolism, the absolute risk and the absolute numbers of expected events, and the subsequent estimated number of prevented events remain low. Based on existing evidence, screening for thrombophilia is unlikely to be cost-effective. However, the potential cost-effectiveness of thrombophilia screening may be improved if the screening strategies were to be refined through more accurate assessment of personal or family history of venous thromboembolism or the introduction of a more global coagulation test for screening.

Thrombophilia and the Risk for Venous Thromboembolism during Pregnancy, Delivery, and Puerperium

The main inherited thrombophilias (antithrombin deficiency, protein C and S deficiency, FVL, the prothrombin gene variant, and MTHFR C677T homozygotes) have a combined prevalence in Western European populations of 15% to 20%. One or more of these inherited thrombophilias is usually found in approximately 50% of women who have a personal history of VTE. Obstetricians must therefore be aware of the interaction between thrombophilias and the procoagulant state of pregnancy and should have an understanding of additional risk factors that may act synergistically with thrombophilias to induce VTE. Such knowledge combined with the appropriate use of thromboprophylaxis and treatment in women who have objectively confirmed VTE continue to improve maternal and perinatal outcomes.

Internal Jugular Vein Thrombosis following Mild Ovarian Hyperstimulation Syndrome in Women with Factor V Leiden Mutation

OBJECTIVE

To study two women who presented with internal jugular vein thrombosis that developed shortly after in vitro fertilization (IVF) therapy complicated by mild ovarian hyperstimulation syndrome (OHSS).

METHODS

Evaluation of the past medical history, treatment, laboratory studies, and clinical outcome of both patients.

RESULTS

The two patients were found to be carriers for factor V Leiden mutation (FVLM). One was homozygote and the other heterozygote for that mutation. The genetic predisposition probably contributed to the development of an early thrombosis in these patients despite the mildness of their OHSS. In the homozygote patient, the dose of low molecular weight heparin was reduced due to vaginal bleeding. Afterwards, fetal loss due to an extensive placental infarction occurred. Infarction was confined to maternal side while the fetal side vessels were spared.

CONCLUSION

We suggest that women of European descent, especially those with personal or familial history of thromboembolic events, should be screened for FVLM before IVF treatment. In those found to be carriers of FVLM, preventive anticoagulation should be considered.

Hormones and cardiovascular health in women

Cardiovascular diseases (CVDs) may have their origin before birth: the combination of being small at birth and having an overly rich post-natal diet increases the likelihood of obesity and of acquiring a specific metabolic syndrome in adulthood that carries an increased risk of CVD. The incidence of CVD and mortality is very low in women of reproductive age but rises to a significant level in older women. In this article, we discuss CVD in relation to hormonal contraception, pregnancy and polycystic ovarian syndrome (PCOS) in younger women and menopause in older women. Women with PCOS have a higher risk of diabetes and hypertension, but studies to date have not shown an effect on CVD events. Use of combined hormonal contraception has only small effects on CVD because of the low baseline incidence of myocardial infarction (MI), stroke and venous thromboembolism (VTE) among young women. Women with existing risk factors or existing CVD, however, should consider alternative contraception. In pregnancy, CVD is rare, although, in the West, it now accounts for a significant proportion of maternal mortality as the frequency of obstetrical causes of mortality has substantially declined. The frequency of VTE is 15 per 10,000 during pregnancy and the post-partum period. In older women, menopause causes a slightly higher risk of MI after allowing for age, although there is substantial heterogeneity in the results of studies on menopause and age at menopause and MI. A larger effect might have been expected, because estrogen reduces the risk of developing atherosclerosis in premenopausal women, whereas in post-menopausal women who may have established atherosclerotic disease, estrogen increases the risk of myocardial disease through the effects on plaque stability and clot formation. Recent trial results indicate that hormone treatment in menopause does not favourably affect the risk of MI, stroke or other vascular disease. Thus, prevention of CVD should rely on diet and fitness, low-dose aspirin and treatment of hypertension, hyperglycaemia and hyperlipidaemia.

Screening for thrombophilia in high-risk situations: a meta-analysis and cost-effectiveness analysis

Laboratory testing for the identification of heritable thrombophilia in high-risk patient groups have become common practice; however, indiscriminate testing of all patients is unjustified. The objective of this study was to evaluate the cost-effectiveness of universal and selective history-based thrombophilia screening relative to no screening, from the perspective of the UK National Health Service, in women prior to prescribing combined oral contraceptives and hormone replacement therapy, women during pregnancy and patients prior to major orthopaedic surgery. A decision analysis model was developed, and data from meta-analysis, the literature and two Delphi studies were incorporated in the model. Incremental cost-effectiveness ratios (ICERs) for screening compared with no screening was calculated for each patient group. Of all the patient groups evaluated, universal screening of women prior to prescribing hormone replacement therapy was the most cost-effective (ICER 6824 pounds). In contrast, universal screening of women prior to prescribing combined oral contraceptives was the least cost-effective strategy (ICER 202,402 pounds). Selective thrombophilia screening based on previous personal and/or family history of venous thromboembolism was more cost-effective than universal screening in all the patient groups evaluated.

Thrombophilia Testing in Patients with Venous Thrombosis

BACKGROUND

Routine thrombophilia testing is controversial because of the low yield of positive tests, costs involved, and debate about the clinical usefulness of the data obtained from testing. Laboratory investigations are rarely done for those with superficial venous thrombosis (SVT) or isolated calf vein thrombosis (CVT) which are often not treated with anticoagulants.

OBJECTIVE

To identify the incidence of markers of thrombophilia in patients with deep vein thrombosis (DVT), SVT, isolated CVT or a history of thrombosis in a referral practice.

METHODS

One hundred and sixty-six patients were referred to our thrombosis unit for consultation, including patients with SVT, DVT, and preoperative patients with a previous history of SVT or DVT. Patients underwent thrombophilia screening and patients with a diagnosis of SVT or DVT were confirmed by bilateral duplex ultrasonography of all lower limb veins. Thrombophilia testing included factor V Leiden (FVL), prothrombin 20210A mutation (P2), methylene tetrahydrofolate reductase deficiency (MTHFR), fasting serum homocysteine (HC), lupus anticoagulant (LA), anticardiolipin antibodies (ACA), antithrombin deficiency (AT), protein S deficiency (PS), and protein C deficiency (PC).

RESULTS

The incidence of any significant abnormality in patients with DVT was 27/44 (61%; 95% Confidence interval [CI], 47-76%) and 10 of these patients were positive for FVL (23%; 95% CI, 10-35%). Twelve patients with isolated CVT were seen and five had at least one abnormality (42%; 95% CI, 14-70%) including one with FVL (8%; 95% CI, 0-24%). Thirty-nine patients with isolated SVT were seen including 14 with at least one abnormality (36%; 95% CI, 21-51%) and five of these patients with SVT had FVL (13%; 95% CI, 2-23%). Nine patients with recurrent DVT were seen and five of these had at least one abnormal test (56%; 95% CI, 23-88%). Finally, 18 of the 166 patients had more than one abnormality (11%; 95% CI, 6-16%).

CONCLUSION

The presence of one or more markers of thrombophilia was significantly higher in this patient population compared to reports from other centres. This study identified 18/166 (10.8%; 95% CI, 6-16%) with more than one defect where life-long anticoagulation might be considered. The results in this subset of patients as well as the serious defects found in some patients with provoked DVT, isolated CVT or isolated SVT demonstrate the value of this screening program to both these patients and their blood relatives. On the other hand, this is a small series from a referral practice where the incidence of these defects is greater than one would expect in the general population. These studies are preliminary and it is not recommended that all VTE patients should be screened on the basis of the current report.

The Relationship of the Factor V Leiden Mutation and Pregnancy Outcomes for Mother and Fetus

OBJECTIVE

We sought to estimate the frequency of pregnancy-related thromboembolic events among carriers of the factor V Leiden (FVL) mutation without a personal history of thromboembolism, and to evaluate the impact of maternal and fetal FVL mutation carriage or other thrombophilias on the risk of adverse outcomes.

METHODS

Women with a singleton pregnancy and no history of thromboembolism were recruited at 13 clinical centers before 14 weeks of gestation from April 2000 to August 2001. Each was tested for the FVL mutation, as was the resultant conceptus after delivery or after miscarriage, when available. The incidence of thromboembolism (primary outcome), and of other adverse outcomes, was compared between FVL mutation carriers and noncarriers. We also compared adverse outcomes in a secondary nested carrier-control analysis of FVL mutation and other coagulation abnormalities. In this secondary analysis, we defined carriers as women having one or more of the following traits: carrier for FVL mutation, protein C deficiency, protein S deficiency, antithrombin III deficiency, activated protein C resistance, or lupus anticoagulant-positive, heterozygous for prothrombin G20210A or homozygous for the 5,10 methylenetetrahydrofolate reductase mutations. Carriers of the FVL mutation alone (with or without activated protein C resistance) were compared with those having one or more other coagulation abnormalities and with controls with no coagulation abnormality.

RESULTS

One hundred thirty-four FVL mutation carriers were identified among 4,885 gravidas (2.7%), with both FVL mutation status and pregnancy outcomes available. No thromboembolic events occurred among the FVL mutation carriers (0%, 95% confidence interval 0-2.7%). Three pulmonary emboli and one deep venous thrombosis occurred (0.08%, 95% confidence interval 0.02-0.21%), all occurring in FVL mutation noncarriers. In the nested carrier-control analysis (n = 339), no differences in adverse pregnancy outcomes were observed between FVL mutation carriers, carriers of other coagulation disorders, and controls. Maternal FVL mutation carriage was not associated with increased pregnancy loss, preeclampsia, placental abruption, or small for gestational age births. However, fetal FVL mutation carriage was associated with more frequent preeclampsia among African-American (15.0%) and Hispanic (12.5%) women than white women (2.6%, P = .04), adjusted odds ratio 2.4 (95% confidence interval 1.0-5.2, P = .05).

CONCLUSION

Among women with no history of thromboembolism, maternal heterozygous carriage of the FVL mutation is associated with a low risk of venous thromboembolism in pregnancy. Neither universal screening for the FVL mutation, nor treatment of low-risk carriers during pregnancy is indicated.

LEVEL OF EVIDENCE

II-2.

Thrombophilia screening in pregnancy

Thromboembolism in pregnancy is a major contributor to pregnancy morbidity and mortality with potentially serious adverse effects for both mother and fetus. The purposes of this article are to explore the impact of heritable and acquired thrombophilias on pregnancy and to determine the appropriateness of screening for thrombophilias in pregnancy. In determining the appropriateness of screening, attention was given to the changes that occur in the coagulation and fibrinolytic systems during normal pregnancy. The impact of different heritable and acquired thrombophilias on maternal venous thromboembolism, fetal loss, and its impact on certain obstetric conditions are then explored. Guidelines and conclusions are made as to the appropriateness of screening.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to list the various thrombophilias associate with pregnancy, to describe the impact of thrombophilias on pregnancy, and to outline the appropriate screening guidelines for thrombophilias during pregnancy.

Risk of venous thromboembolic disease in women

OBJECTIVES

To review the scientific evidence on the risk and prevention of venous thromboembolic disease (VTD) associated with specific clinical factors in women.

STUDY DESIGN

Qualitative systematic review.

DATA SOURCE

MEDLINE, Cochrane library, clinical practice guidelines, and referenced articles from these sources.

RESULTS

Gender is not an independent risk factor of VTD. Absolute risks associated with each circumstance (per 1000 women-year) were: pregnancy, 1.23; puerperium, 3.2; pregnancy in thrombophilic, 40; pregnancy and background of previous VTD, 110; use of third generation contraceptives, 0.3; postcoital pill, no risk; hormone replacement therapy, 0.2-5.9; tamoxifen, 3.6-12; and raloxifene, 9.5. The quality of the evidence on risk was classified as good or excellent. Evidence on prevention was scarce. Screening for thrombophilia prior to the prescription of contraceptives is not cost-effective as a strategy for prophylaxis. Use of low molecular weight heparin (LMWH) in high-risk pregnancies is supported by medium quality studies.

CONCLUSIONS

There is good quality evidence on the magnitude of VTD risk associated with specific clinical factors in women. No studies on the utility of preventive measures have been performed for most of these circumstances. There is no evidence about the risk associated with the combination of several risk factors.

Thromboembolism in pregnancy

PURPOSE OF REVIEW

Venous thromboembolism is the leading cause of maternal death in the UK. Thrombophilia underlies many thrombotic disorders in pregnancy. The high prevalence of thrombophilic defects in the population, the association of defects with venous thromboembolism and the special considerations for management make it a widely debated subject.

RECENT FINDINGS

A limited number of studies measuring the risk of venous thromboembolism in pregnancy with thrombophilia have been conducted within the last year. Studies confirm that heritable thrombophilias are associated with increased risk of venous thromboembolism in pregnancy. However, estimated risks vary between individual studies. The risk of venous thromboembolism with acquired thrombophilia remains unclear. Guidelines have been published to guide clinicians in preventing and treating venous thromboembolism in pregnancy; however, large-scale, randomized controlled trials need to be conducted to establish the effectiveness of administering antithrombotic agents in pregnancy. Although selective thrombophilia screening based on prior history of venous thromboembolism has been proposed, the overall clinical and economic benefit of universal and selective screening is unsupported.

SUMMARY

Due to the lack of studies, gaps still exist in our knowledge of the risk of pregnancy-related venous thromboembolism associated with thrombophilia. In particular, accurate estimates are required for the risks of acquired thrombophilias. Furthermore, the true effectiveness of anticolagulants in pregnancy needs to be established through well-conducted studies and randomized controlled trials. These studies will inform clinicians and help to determine the optimum management and prevention strategies for thrombophilia and venous thromboembolism in pregnancy.

Thrombophilia and adverse pregnancy outcome

PURPOSE OF REVIEW

Recent case-control studies and metaanalyses have attempted to quantify the risks associated with individual thrombophilic defects and adverse clinical events in pregnancy, including fetal loss, preeclampsia, placental abruption and intrauterine growth restriction. This review has examined the evidence.

RECENT FINDINGS

The literature is in general agreement that thrombophilia increases the risk of venous thromboembolism and adverse pregnancy outcomes, including pregnancy loss, preeclampsia, placental abruption and intrauterine growth restriction in pregnancy. However, the size of the estimated risks varies between individual studies due to heterogeneity in study design. Low-molecular-weight heparin has been shown to be the superior choice, on the grounds of safety and effectiveness, in preventing venous thromboembolism and improving pregnancy loss. Large-scale, randomized controlled studies are required, however, to confirm these findings. Although selective thrombophilia screening based on prior venous thromboembolism history has been shown to be marginally more cost-effective than universal screening in pregnancy, the overall clinical and economic benefit of universal and selective screening is unsupported.

SUMMARY

Despite the growing evidence in the literature, there are still gaps in our knowledge of thrombophilia and pregnancy. In particular, accurate estimates are required of the risks of venous thromboembolism and adverse pregnancy outcomes associated with some thrombophilias and the relative clinical and cost-effectiveness of different anticoagulation therapies in the prevention of venous thromboembolism and pregnancy loss. More large-scale studies are required to better inform clinicians and help determine optimum management and prevention strategies of thrombophilia and associated adverse clinical events in pregnancy.

Genetic thrombophilia

The genetic thrombophilias are an important cause of venous thrombotic events. Much has been learned about the natural history of these disorders, their genetics, and, to a lesser degree, their treatment. This article provides an overview of the genetics of thrombophilia. Specific information on the factor V Leiden mutation;the prothrombin G20210A mutation; and protein C, proteinS, and antithrombin deficiency is reviewed. Current testing and treatment options for the genetic thrombophilias also are discussed.

High frequency of congenital thrombophilia in women with pathological pregnancies?

The obstetrical complications preeclampsia, intrauterine growth restriction (IUGR), placental abruption and fetal loss are major causes of maternal and fetal morbidity and mortality. Much recent research has focused on to what extent congenital thrombophilia contributes to these obstetrical complications. Combined with the hypercoagulable state of pregnancy, thrombophilia has the potential to induce placental thrombosis and cause placental insufficiency with subsequent obstetrical complications. This article aims to review and discuss published clinical studies of the relationship between congenital thrombophilia and preeclampsia, IUGR, placental abruption and fetal loss. In addition, the few published clinical trials of prophylactic antithrombotic treatment to prevent severe obstetrical complications in thrombophilic women are discussed. The studies have shown variable results evaluated mainly as a result of the limited number of case reports published. However, the strongest association was found to be between congenital thrombophilia and preeclampsia and late fetal loss. Early fetal loss was not found to be associated with congenital thrombophilia. At present, the question remains open as to whether IUGR and placental abruption is directly associated with thrombophilia or mediated through preeclampsia. In conclusion, the associations between congenital thrombophilia and preeclampsia, IUGR, placental abruption and fetal loss only reaches evidence grade 4. Present recommendations and clinical guidelines are thus based on weak scientific proof.

Prevalence of thrombophilia in women with severe ovarian hyperstimulation syndrome and cost-effectiveness of screening

OBJECTIVE

To determine the prevalence of markers of thrombophilia in patients with severe ovarian hyperstimulation syndrome (OHSS) and to evaluate the cost-effectiveness of screening for factor V Leiden and prothrombin G20210A mutations in women entering an IVF program.

DESIGN

Case-control study and cost-effectiveness analysis.

SETTING

University teaching hospital.

PATIENT(S)

Women undergoing controlled ovarian hyperstimulation for IVF complicated by severe OHSS (group 1, n = 20), women undergoing controlled ovarian hyperstimulation for IVF without development of severe OHSS (group 2, n = 40), and healthy control subjects (group 3, n = 100).

INTERVENTION(S)

Investigation of markers of thrombophilia. Estimate of number of IVF patients needed to detect a case of severe OHSS and thrombosis associated with thrombophilia genetic mutation was calculated from the available data.

MAIN OUTCOME MEASURE(S)

Blood samples were analyzed for inherited (resistance to activated protein C due to the factor V Leiden mutation; prothrombin G20210A mutation; deficiencies in antithrombin, protein C, and protein S) and acquired (presence of circulating lupus anticoagulants and/or anticardiolipin antibodies; deficiencies of antithrombin and protein S; acquired protein C resistance) markers of thrombophilia. The cost of preventing one thrombotic event in a patient developing severe OHSS after IVF and having factor V Leiden or prothrombin G20210A mutations was calculated.

RESULT(S)

None of the OHSS patients or controls had antithrombin, protein C, or free protein S deficiencies. All of them tested negative for antiphospholipid antibodies. No patient in group 1 had the factor V Leiden or prothrombin G20210A mutations. The prothrombin G20210A mutation was detected in 1 out of 40 patients (2.5%) in group 2. Both factor V Leiden and prothrombin G20210A mutations were detected in two of the control subjects (2%) (group 3). The estimated cost of preventing one thrombotic event arising as a consequence of screening for factor V Leiden and prothrombin G20210A mutation is a minimum of 418,970 dollars and 2,430,000 dollars, respectively.

CONCLUSION(S)

The prevalence of thrombophilia is not increased in women with severe OHSS. Screening for V Leiden and prothrombin G20210A mutation in an IVF general population is not cost-effective.

Genetic testing for cardiovascular disease susceptibility: a useful clinical management tool or possible misinformation?

Genetic susceptibility tests are already advertised on the Internet to identify individuals at above average risk for cardiovascular disease (CVD), such as deep vein thrombosis, hyperlipidemia, or atherosclerosis, whereas other tests claim to predict response to a particular drug treatment. Some kits are available to the public directly, bypassing a doctor. Their value, however, must be considered carefully, because although a genotype may be strongly and consistently associated with an intermediate trait, and because the intermediate trait is a strong predictor of CVD risk, there may be little or no association of genotype with risk over and above that of the measured trait. This is because multigenic effects and environmental modification (context dependency) of genotype effects determine CVD risk. An individual's personal characteristics and plasma risk-trait levels (which reflect both genotype and exposure) at present are the best predictors of clinical outcome. Only when genetic tests surpass this, possibly by the inclusion of many functional common variants, in conjunction with their context-dependent effects on risk, might their usefulness in clinical management be realized. Here we review some of the particular issues and concerns raised by CVD-risk genetic testing, and suggest areas of further research to address these issues.

Inherited and acquired thrombophilias and poor pregnancy outcome: should we be treating with heparin?

PURPOSE OF REVIEW

The most important acquired thrombophilia related to poor pregnancy outcome is probably antiphospholipid syndrome. Inherited thrombophilias that have been implicated in venous thromboembolism and poor pregnancy outcome and for which standard tests are generally available are antithrombin III deficiency, the factor V Leiden mutation, prothrombin G20210A mutation and the C677T polymorphism in the methylenetetrahydrofolate reductase system implicated in mild hyperhomocysteinaemia. The management of antiphospholipid syndrome with previous fetal losses is well documented and substantiated by small clinical trials. It is the purpose of this review to investigate new contributions to this field since June 2002.

RECENT FINDINGS

Only one randomized trial was published during the review period, but a Cochrane review and several excellent review articles appeared detailing management.

SUMMARY

There is a dire lack of randomized trials in the literature on the efficacy of heparin or other coagulation modulators on pregnancy outcome in patients with inherited thrombophilias. There is consensus on thrombo-prophylaxis for antiphospholipid syndrome. Protocols for the management of venous thromboembolism and pulmonary emboli related to pregnancy are well established.

Cerebrovascular Disease in Pregnancy

Stroke during pregnancy is a special category of stroke in young women. Although the absolute risk is small, there are diverse causes, including those inherent to the pregnant state, that may have a significant impact on maternal and fetal outcome. Severe pre-eclampsia and eclampsia are commonly associated with ischemic and hemorrhagic stroke, but must not be presumed the sole cause of stroke in pregnant women. Magnesium sulfate is the treatment of choice to prevent eclampsia. Randomized clinical trials in pregnant women are not available to provide guidance for the treatment of ischemic and hemorrhagic stroke in pregnant women. Various antithrombotic agents may be safely used during specific stages of pregnancy for treatment and prevention of ischemic stroke, with low-dose aspirin, unfractionated heparin, and low molecular weight heparin the preferred agents. Low molecular weight heparin may be safer than unfractionated heparin. Treatment of parenchymatous intracerebral hemorrhage and subarachnoid hemorrhage during pregnancy and the puerperium must be individualized. Aneurysms may be treated with neurosurgical clipping or endovascular coiling, depending on neurosurgical considerations. Cesarean or vaginal delivery may be used depending on the timing of delivery, adequacy of aneurysm occlusion, and risk to mother and fetus. Arteriovenous malformations are best treated in a multimodal fashion at a specialized treatment center.

Factor V Leiden: a review of the literature

Factor V Leiden, formed by a genetic mutation, disrupts the body's anticoagulation defense system. It was isolated as recently as 1994 as a risk factor for venous thromboembolism. Factor V Leiden has also been linked to preeclampsia, pregnancy loss, and fetal growth restriction. In addition, factor V Leiden has implications for women who are not pregnant. The most effective screening tool is a thorough personal and family history related to thrombosis. For women with a positive factor V Leiden screen, counseling regarding the risks of thrombosis is essential.

Inherited thrombophilia and venous thromboembolism

Pulmonary thromboembolism (PTE) is the major cause of maternal death in the UK. Underlying PTE is the problem of deep venous thrombosis (DVT). Inherited thrombophilia will be found in about 50% of women with a personal history of venous thromboembolism (VTE), and screening for thrombophilia should be considered in women with a personal or family history of VTE. There is currently no place for universal screening for thrombophilia in pregnancy. There are particular considerations with regard to the management of thrombophilia in pregnancy. Low-molecular-weight heparins are now the heparin of choice in pregnancy because of a better side-effect profile (substantially reduced risk of heparin-induced osteoporosis and heparin-induced thrombocytopaenia) compared to unfractionated heparin, good safety record for mother and fetus and convenient once-daily dosing for prophylaxis.

Prevention of venous thromboembolism in pregnancy

Pulmonary thromboembolism, rising from deep venous thrombosis (DVT), is a major cause of maternal death in the developed World. DVT is a significant source of morbidity in pregnancy and the puerperium with long-term sequelae such as post-thrombotic syndrome. The major risk factors for venous thromboembolism (VTE) are: increasing age, particularly over 35 years; operative vaginal delivery; Caesarean section, especially emergency Caesarean section in labour; high body mass index; previous VTE, especially if idiopathic or thrombophilia-associated; thrombophilia; and a family history of thrombosis suggestive of an underlying thrombophilia. Thromboprophylaxis centres largely on the use of low-molecular-weight heparin (LMWH). LMWHs, such as enoxaparin and dalteparin, have substantial clinical and practical advantages compared with unfractionated heparin, particularly in terms of improved safety with a significantly lower incidence of heparin-induced osteoporosis and thrombocytopenia. Such agents should be used in women with significant risk factors for VTE both antenatally and post-partum.

Prevention and management of venous thromboembolism in pregnancy

Pulmonary thromboembolism is a major cause of maternal mortality. DVT causes significant morbidity in pregnancy and in later life owing to the post-thrombotic syndrome. Obstetricians must have an understanding of the risk factors for VTE, the appropriate use of prophylaxis, the need for objective diagnosis in women with suspected VTE, and the appropriate use of anticoagulant therapy. Greater use of prophylaxis is needed after vaginal delivery. Because acute VTE is relatively uncommon, greater use of proposed guidelines [24,84,85] may be of value in improving management, but the involvement of clinicians with expertise in the management of these cases is also important.

Thrombophilia: implications for pregnancy outcome

There is growing evidence implicating congenital and acquired thrombophilias in the pathophysiological processes underlying miscarriage, intrauterine growth restriction (IUGR) and pre-eclampsia. Pregnancy itself is notably a hypercoagulable state, at least in part, due to the physiological changes in the coagulation and fibrinolytic systems; this has the potential for interaction with an acquired or heritable thrombophilia to cause adverse experiences. Recurrent fetal loss is associated with antiphospholipid antibody syndrome, procoagulant platelet microparticles and some inherited thrombophilias such as Factor V Leiden. There have been reports of both heritable and acquired thrombophilias being associated with pre-eclampsia, IUGR and abruption. However, these associations are not consistently reported with hereditary thrombophilias. The presence of thrombophilia might influence the severity of a condition such as pre-eclampsia, rather than cause it. The risk of fetal loss related to antiphospholipid syndrome can be reduced with antithrombotic therapy with heparin and low dose aspirin. Whether this extends to other thrombophilic conditions associated with adverse pregnancy outcome is not clear and further investigation is required. Screening for, and finding a, thrombophilic disease in patients with problems such as recurrent miscarriage, intrauterine death, intrauterine growth restriction and pre-eclampsia, may reflect an increased risk of venous thromboembolism (VTE).