The risk of pregnancy-related venous thromboembolism in women who are homozygous for factor V Leiden

The risk of venous thromboembolism (VTE) is increased in pregnancy and during the post-partum period. The absolute risk for pregnancy-related VTE in heterozygous women with the factor V Leiden mutation is approximately 2%, but studies on this risk for homozygous women show conflicting results. In a retrospective family study, we found that the risk of pregnancy-related VTE in women with a symptomatic first-degree relative was 17% per pregnancy (95%CI 4.7-37.4). Anticoagulant prophylaxis during the post-partum period appears to be indicated in asymptomatic homozygous women from symptomatic kindred, whereas this could be decided on an individual basis during pregnancy.     

Clinical and laboratory expression of associated thrombophilic conditions (homozygous/heterozygous factor V Leiden mutation and heterozygous prothrombin variant 20210A) in an Italian family.

Prothrombin variant 20210A is maintained to be a mild risk factor for venous thromboembolism (VTE). The association of this defect with other inherited thrombophilic conditions may result in an increased risk of developing VTE. In this article, a family is described in which prothrombin variant was associated with either homozygous or heterozygous factor V Leiden (FV Leiden) mutation. All family members except the proband were asymptomatic despite the presence and the severity of the underlying genetic defect(s). The proband, who carried homozygous FV Leiden mutation and heterozygous prothrombin variant, experienced recurrent VTE during pregnancies, whereas one brother, with the same defect, was asymptomatic. Mean prothrombin antigen and activity levels were higher in carriers of the prothrombin variant as compared with noncarriers. Thrombin generation was assessed in family members, in carriers of prothrombin variant or homozygous FV Leiden mutation and in a control group. Most of the family members presented with increased prothrombin fragment 1+2 levels possibly because of the presence of the FV Leiden mutation. Although it is conceivable that the co-inheritance of prothrombin variant and FV Leiden mutation may increase the risk of VTE, patients with these combined defects may remain asymptomatic. It is likely that acquired triggering conditions play a major role in determining VTE in carriers of a mild genetic predisposition. This has to be taken into account when recommendation for thromboprophylaxis is given.     

Incidence of venous thromboembolism in asymptomatic family members who are carriers of factor V Leiden: a prospective cohort study

In a prospective cohort study, we assessed the incidence of spontaneous and risk period-related venous thromboembolism (VTE) in asymptomatic family members of patients who experienced VTE and had the factor V Leiden mutation. In all, 561 family members of 131 probands were included, 313 of whom were carriers (299 heterozygous and 14 homozygous) and 248 of whom were noncarriers of the factor V Leiden mutation. Average follow-up was 4 years (range, 4 months-6 years). There were 1255 and 984 observation-years of follow-up in carriers and noncarriers, respectively. Eight episodes of VTE occurred in heterozygous carriers, resulting in an annual incidence of 0.67% (95% confidence interval [CI], 0.29-1.33). Two events occurred in the absence of associated risk factors, determining an annual incidence of spontaneous VTE of 0.17% (95% CI, 0.02-0.6). Only one VTE (risk period-related) occurred in noncarriers, with an annual incidence of 0.1% (95% CI, 0.003-0.56). Relative risk for VTE in heterozygous carriers compared with noncarriers of the factor V Leiden mutation was 6.6 (95% CI, 1.1-39.8). Risk period-related VTE occurred with an incidence of 18% and 5% per risk period in heterozygous carriers and in noncarriers, respectively. Thus, the low rate of VTE in asymptomatic family members carrying the mutation did not justify continuous anticoagulant prophylaxis. Screening families of symptomatic probands with the factor V Leiden mutation has the potential to identify those asymptomatic carriers who might benefit from thromboprophylaxis during risk periods.     

Factor V Leiden: the venous thrombotic risk in thrombophilic families

Factor V Leiden (FVL) leads to a sevenfold increased risk of venous thrombosis and is present in 50% of individuals from families referred because of unexplained familial thrombophilia. We assessed the association of FVL with venous thromboembolism (VTE) in 12 thrombophilic families of symptomatic probands with FVL in a retrospective follow-up study. We screened 182 first- and second-degree relatives of the 12 unrelated propositi for the FVL mutation and the occurrence of VTE. The incidence rate of VTE in carriers of FVL (0.56%/year) was about six times the incidence for the Dutch population (0.1%/year). The incidence rate in non-carriers also appeared to be higher (0.15% per year). At the age of 50 years, the probability of not being affected by VTE was reduced to 75% for carriers and to 93% for non-carriers (P = 0.009). Identification of carriers of FV Leiden may be worthwhile in young symptomatic individuals and their relatives with a strong positive family history of venous thromboembolism or a history of recurrent venous thrombosis who may be at risk (e.g. pregnancy, use of oral contraceptives). After adjustment for prothrombin G20210A (present in two families), even higher thrombotic incidence rates were found in carriers and non-carriers of FVL. This makes the presence of other unknown prothrombotic risk factors more probable in these families.     

Thrombotic risk during oral contraceptive use and pregnancy in women with factor V Leiden or prothrombin mutation: a rational approach to contraception

Current guidelines discourage combined oral contraceptive (COC) use in women with hereditary thrombophilic defects. However, qualifying all hereditary thrombophilic defects as similarly strong risk factors might be questioned. Recent studies indicate the risk of venous thromboembolism (VTE) of a factor V Leiden mutation as considerably lower than a deficiency of protein C, protein S, or antithrombin. In a retrospective family cohort, the VTE risk during COC use and pregnancy (including postpartum) was assessed in 798 female relatives with or without a heterozygous, double heterozygous, or homozygous factor V Leiden or prothrombin G20210A mutation. Overall, absolute VTE risk in women with no, single, or combined defects was 0.13 (95% confidence interval 0.08-0.21), 0.35 (0.22-0.53), and 0.94 (0.47-1.67) per 100 person-years, while these were 0.19 (0.07-0.41), 0.49 (0.18-1.07), and 0.86 (0.10-3.11) during COC use, and 0.73 (0.30-1.51), 1.97 (0.94-3.63), and 7.65 (3.08-15.76) during pregnancy. COC use and pregnancy were independent risk factors for VTE, with highest risk during pregnancy postpartum, as demonstrated by adjusted hazard ratios of 16.0 (8.0-32.2) versus 2.2 (1.1-4.0) during COC use. Rather than strictly contraindicating COC use, we advocate that detailed counseling on all contraceptive options, including COCs, addressing the associated risks of both VTE and unintended pregnancy, enabling these women to make an informed choice.     

Thrombophilia and pregnancy

The risk of venous thromboembolism (VTE) increases up to 5-10-fold during pregnancy and VTE represents the first cause of maternal mortality. The annual incidence of VTE is 0.97 per 1000 women during pregnancy and 7.19 per 1000 in the puerperium. The risk is higher in carriers of inherited thrombophilia. Prophylaxis of VTE during pregnancy in thrombophilic women, is still controversial, whereas there is agreement on the used of LMWH or oral anticoagulants during puerperium. LMWH is suggested during pregnancy in antithrombin deficient women, compound heterozygotes for prothrombin G20210A and factor V Leiden, and homozygotes for these conditions, with no prior VTE. In heterozygotes for F V Leiden or prothrombin G20210A with no prior VTE surveillance is preferred during pregnancy and LMWH or OA during puerperium. For patients with APLAs and no prior VTE or fetal loss, one of the following approaches is suggested: prophylactic LMWH and/or low-dose aspirin, mini dose heparin, surveillance (7 degrees ACCP). Patients with APLAs and a history of thrombosis should receive therapeutic-dose LMWH or UH plus low-dose aspirin during pregnancy and long term OA postpartum. In women with prior VTE and inherited thrombophilia, prophylactic or intermediate-dose LMWH is recommended during pregnancy plus post-partum OA. Intermediate-dose LMWH during pregnancy is suggested in antithrombin-deficient women, compound heterozygotes for prothrombin G20210A and factor V Leiden, and homozygotes for these conditions.     

Risk of thrombosis associated with oral contraceptives of women from 97 families with inherited thrombophilia: high risk of thrombosis in carriers of the G20210A mutation of the prothrombin gene

BACKGROUND AND OBJECTIVES: Oral contraceptives (OC) and inherited thrombophilia are well-known risk factors associated with venous thromboembolism (VTE). However, there are only few studies on the risk of VTE in women with inherited thrombophilia who use oral contraceptives. DESIGN AND METHODS: We performed a retrospective family cohort study of 325 women belonging to 97 families with inherited thrombophilia, including antithrombin, protein S and C deficiencies, the factor V Leiden mutation (FVL) and the G20210A mutation of the prothrombin gene (PT20210A) to determine the risk of VTE associated with OC intake. RESULTS: For carriers of the PT20210A mutation, the risk of VTE in OC users was 3-fold higher (95% CI 1.3-6.8) than that in non-carriers. Carriers of FVL mutation taking OC showed an OR of 1.4 (95% CI 0.6-3.3), indicating a tendency to increase the risk of VTE. INTERPRETATION AND CONCLUSIONS: Because of the high prevalence of the PT20210A (6.5%) and FVL (2%) mutations in the general Spanish population and the increased risk of VTE associated with OC intake, genetic screening for these mutations should be considered in potential OC users belonging to families with thrombophilia.     

Prothrombin fragment 1+2 and thrombin–antithrombin complex levels in patients with inherited APC resistance due to factor V Leiden mutation

Inherited activated protein C (APC) resistance is a newly described pathological condition associated with familial thrombophilia. A recent report on a family with APC resistance showed increased levels of prothrombin fragment 1+2 (F1+2) in the affected individuals. No data concerning thrombin–antithrombin complex (TAT) levels in patients with inherited APC resistance are presently available. The aim of this study was to assess the plasma levels of F1+2 and TAT in patients with inherited APC resistance due to factor V (F.V) Leiden mutation and to evaluate F1+2 and TAT levels in symptomatic and asymptomatic patients with the defect (‘carriers’) as compared to their family members having no evidence of F.V Leiden mutation (‘non-carriers’). One hundred and twenty-nine individuals belonging to 30 families with inherited APC resistance due to F.V Leiden mutation were studied. F1+2 and TAT levels were determined using two commercially available ELISA kits and cut-off values were defined as the higher limits of normal ranges obtained in healthy volunteers. Out of the 129 family members investigated, 36 were non-carriers, 85 were heterozygous and eight homozygous for F.V Leiden mutation. Thrombosis had occurred in 2/36 (6%) non-carriers, in 36/85 (42.3%) heterozygous and in 5/8 (63%) homozygous. Median levels of F1+2 and TAT were above cut-off values in carriers, whereas they were below in non-carriers. An overall percentage of 68.8% of carriers exhibited F1+2 levels above the cut-off value as compared to 38.9% of non-carriers. For TAT, an overall percentage of 63.4% of carriers presented with levels above the cut-off compared with 28% of non-carriers. In conclusion, patients with inherited F.V Leiden mutation may exhibit increased levels of F1+2 and TAT. There are no differences in F1+2 and TAT median levels among symptomatic and asymptomatic carriers. The percentage of carriers of F.V Leiden with levels of F1+2 and TAT above cut-off appears to be higher than that found in other clotting inhibitors defects and in this respect the defect might be considered different. However, these findings and the presence of a high percentage of non-carriers presenting with increased F1+2 and TAT levels may suggest the possible coexistence in these families of other unknown defects predisposing to thrombosis.     

The 4G/4G polymorphism of the hypofibrinolytic plasminogen activator inhibitor type 1 gene: an independent risk factor for serious pregnancy complications

The specific aim of the current study of 133 women with at least 1 pregnancy and measures of hypofibrinolytic and thrombophilic gene mutations was to determine retrospectively whether the mutations were associated with adverse pregnancy outcomes including prematurity, miscarriage, stillbirth, intrauterine growth retardation (IUGR), eclampsia, and abruptio placentae. Four gene mutations (factor V Leiden, methylenetetrahydrofolate reductase [MTHFR], prothrombin, and 4G/5G polymorphism of the plasminogen activator inhibitor type 1 [PAI-1] gene) were assessed by polymerase chain reaction (PCR). One hundred twenty-two women were genotyped for all 4 genes and divided into gene mutation (n = 68) and non-gene (n = 54) groups. The gene mutation group included those with at least 1 thrombophilic mutation (heterozygous for factor V Leiden, heterozygous for prothrombin, and homozygous for MTHFR), or hypofibrinolysis with homozygosity for the 4G polymorphism of the PAI-1 gene. The non-gene mutation group included those with no mutation for all 4 genes (wild-type normal) or who were wild-type normal for the prothrombin and factor V Leiden mutations and heterozygous for MTHFR and/or 4G/5G for the PAI-1 gene, neither heterozygosity associated with coagulation abnormalities. The 68 women with gene mutations, versus 54 in the non-gene mutation group, has more prematurity (10% v 4%, chi2 = 5.4, P = .021), more IUGR (3% v 0%, P = .035), and more total complications of pregnancy (37% v 21%, chi2 = 11.6, P = .001). The number of pregnancies (P = .0001) and 4G/4G polymorphism of the PAI-1 gene (P = .029) were positively associated with complications of pregnancy by stepwise logistic regression when the age, number of pregnancies, and all 4 gene mutations were the explanatory variables. Heritable hypofibrinolysis, mediated by 4G/4G homozygosity for the PAI-1 gene, is an independent significant, potentially reversible risk factor for pregnancy complications, probably acting through thrombotic induction of placental insufficiency.     

The risk of recurrent venous thromboembolism among heterozygous carriers of factor V Leiden or prothrombin G20210A mutation. A systematic review of prospective studies

Factor V Leiden (FVL) and prothrombin G20210A mutation (PTM) are the two most common genetic polymorphisms known to predispose to a first episode of venous thromboembolism (VTE). However, whether these thrombophilic abnormalities are also risk factors for recurrent VTE is unclear. We conducted a systematic review of prospective studies to assess the risk of recurrent VTE associated with heterozygous carriage of each of these mutations. All randomized controlled trials and prospective cohort studies that reported the incidence of recurrent VTE in patients with and without FVL and PTM after discontinuation of anticoagulant treatment were collected and analyzed. The risk ratios (RR) and their 95% confidence intervals (CI) for recurrent VTE were calculated in heterozygous carriers of FVL or PTM and compared to those of non-carriers. Eleven studies fulfilled the inclusion criteria. Recurrent VTE occurred in 114 out of 557 heterozygous carriers of FVL (20.5%) as compared to 382 out of 2,646 non-carriers (14.4%); and in 38 out of 212 heterozygous carriers of PTM (17.9%) compared to 428 of 2,996 non-carriers (14.3%). The RR of VTE recurrence conferred by the heterozygous carriage of FVL and PTM was 1.39 (95% CI, range 1.15 to 1.67) and 1.20 (range 0.89 to 1.61), respectively, using the Mantel-Haenszel fixed-effects model; 1.45 (1.13 to 1.85) and 1.36 (1.02 to 1.82), respectively, using the Der Simonian and Laird random effects method. In symptomatic patients with VTE, heterozygous carriage of FVL is clearly associated with a definitely increased risk of recurrent thromboembolism. The risk is lower with PTM and is difficult to interpret since it varies according to the assessment method used.     

The risk of recurrent venous thromboembolism in pregnancy and puerperium without antithrombotic prophylaxis

Whether or not pregnant women with a previous episode of venous thromboembolism (VTE) should receive antithrombotic prophylaxis is a matter of debate. In order to estimate the rate of recurrent deep venous thrombosis (DVT) or pulmonary embolism (PE) during pregnancy and puerperium we retrospectively investigated a cohort of 1104 women with previous VTE; after a single DVT or isolated PE, 88 of them became pregnant at least once without receiving antithrombotic prophylaxis. Overall, 155 pregnancies and 120 puerperium periods without prophylaxis were recorded. There were nine recurrences during pregnancy and 10 during puerperium, with a rate of 5.8% [95% confidence interval (CI) 3.0-10.6] and 8.3% (95%CI 4.5-14.6) respectively. In pregnancy, the rate of recurrence was 7.5% (95%CI 4.0-13.7) if the first VTE was unprovoked, related to pregnancy or to oral contraceptive use, whereas no recurrence occurred if the first VTE was related to other transient risk factors. In puerperium, the rate of recurrence was 15.5% (95%CI 7.7-28.7) in women with a pregnancy-related first VTE, with a risk 3.9-times higher than in the remaining women. Inherited thrombophilia was not associated with a statistically significant increase in risk of recurrence in pregnancy or in puerperium, yet the rate of recurrence in puerperium was 14.2% (95%CI 5.7-31.4) in overall carriers of factor V Leiden and 30% (95%CI 10.7-60.3) in carriers with a pregnancy-related first VTE, with a risk 6.8 times higher than in women without thrombophilia and with a non pregnancy-related first VTE.     

Increased risk for fetal loss in carriers of the factor V Leiden mutation.

BACKGROUND: An increased risk for fetal loss caused by placental thrombosis is probable in carriers of the factor V Leiden mutation but has not been demonstrated consistently in previous studies. OBJECTIVE: To determine the overall risk for fetal loss and the separate risks for miscarriage and stillbirth in carriers of the factor V Leiden mutation. DESIGN: Retrospective cohort study. SETTING: Three university hospitals. PARTICIPANTS: 228 carriers of the factor V Leiden mutation (77 propositi, 151 relatives) and 121 noncarrier relatives (controls). All participants had been pregnant at least once. MEASUREMENTS: Risks for fetal loss, miscarriage (defined as fetal loss within 20 weeks of gestation), and stillbirth (defined as fetal loss after >20 weeks of gestation) in women and in pregnancies were estimated and compared in carriers and noncarriers. Adjusted odds ratios were calculated by using multiple regression analysis. A random-effects model was used for comparisons of pregnancies. RESULTS: Fetal loss occurred in 31.6% of carriers and 22.3% of noncarriers, miscarriage occurred in 29.4% of carriers and 17.4% of noncarriers, and stillbirth occurred in 5.7% of carriers and 5.0% of noncarriers. Fetal loss recurred in 10.1% of carriers and 4.1% of noncarriers (odds ratio, 2.60 [95% CI, 0.96 to 7.03]). Adjusted odds ratios were 2.12 (CI, 1.35 to 3.33) for fetal loss, 2.08 (CI, 1.33 to 3.25) for miscarriage, and 1.60 (CI, 0.58 to 4.43) for still-birth when pregnancies in carriers and noncarriers were compared. Homozygous carriers had a greater risk for fetal loss (odds ratio, 2.01 [CI, 0.94 to 4.32]) and stillbirth (odds ratio, 4.85 [CI, 0.82 to 25.58]) than heterozygous carriers. CONCLUSIONS: Carriers of the factor V Leiden mutation have a greater risk for fetal loss (particularly miscarriage) than noncarriers. These data further suggest a greater risk for recurrence of fetal loss in carriers than in noncarriers and a greater risk for fetal loss and stillbirth in homozygous carriers than in heterozygous carriers.     

Prothrombin 20210A mutation: a mild risk factor for venous thromboembolism but not for arterial thrombotic disease and pregnancy-related complications in a family study

BACKGROUND: The prothrombin 20210A mutation has been associated with an increased risk of venous thromboembolism (VTE). Its relationship with arterial disease and pregnancy-related complications is, however, still uncertain. The aim of this study was to estimate the incidences of first venous and arterial thrombotic events and pregnancy-related complications in relatives of patients with the mutation. METHODS: After clinical classification, the presence of the mutation was determined in first-degree relatives of consecutive patients with the mutation and a history of VTE or premature atherosclerosis. Relatives with and without the mutation were compared. RESULTS: Of all relatives, 204 (50%) were heterozygous, 5 were homozygous, and 198 had a normal genotype. The annual incidence of a first episode of VTE was 0.35% and 0.18% in carriers and noncarriers, respectively (odds ratio [OR], 1.9; 95% confidence interval [CI], 0.9-4.1); the annual incidence of a first arterial thrombosis was 0.22% and 0.15% in carriers and noncarriers, respectively (OR, 2.3; 95% CI, 0.8-6.3). The annual incidence of a first myocardial infarction was 0.14% (95% CI, 0.05%-0.23%) and 0.05% (0.01%-0.14%) in carriers and noncarriers, respectively (OR, 4.7; 95% CI, 1.0-22.5; P =.06). In particular, homozygous carriers were at increased risk of VTE (OR, 6.0; 95% CI, 1.3-27.2), whereas a history of VTE in the proband influenced the risk of VTE in the relatives. Women with the mutation did not experience significantly more pregnancy-related complications than their relatives with a normal genotype. CONCLUSIONS: The prothrombin mutation is a mild risk factor for VTE within families of carriers but does not seem to play an important role in arterial thrombotic disease, with the exception of myocardial infarction, or in pregnancy-related complications.     

Co-segregation of thrombophilic disorders in factor V Leiden carriers; the contributions of factor VIII,factor XI,thrombin activatable fibrinolysis inhibitor and lipoprotein(a) to the absolute risk of venous thromboembolism

BACKGROUND AND OBJECTIVES: The clinical expression of factor V Leiden varies widely within and between families and only a minority of carriers will ever develop venous thromboembolism. Co-segregation of thrombophilic disorders is a possible explanation. Our aim was to assess the contributions of high levels of factor VIII:C, factor XI:C, thrombin activatable fibrinolysis inhibitor (TAFI) and lipoprotein (a) (Lp(a)) to the risk of venous thromboembolism in factor V Leiden carriers. DESIGN AND METHODS: Levels of the four proteins were measured, in addition to tests of deficiencies for antithrombin, protein C and protein S, and the prothrombin G20210A mutation, in 153 factor V Leiden carriers, derived from a family cohort study. The (adjusted) relative risk and absolute risk of venous thromboembolism for high levels of each protein were calculated. RESULTS: Of carriers, 60% had one or more concomitant thrombophilic disorders. Crude odds ratios (95% CI) of venous thromboembolism for high protein levels were: 3.2 (1.1-9.3) (factor VIII:C); 1.7 (0.6-4.9) (factor XI:C); 3.0 (1.1-8.2) (TAFI); and 1.9 (0.7-5.7) (Lp(a)). Adjusted for age, sex, other concomitant thrombophilic disorders and exogenous risk factors, the odds ratio for venous thromboembolism were 2.7 (0.8-8.7) for high factor VIII:C levels and 1.8 (0.6-5.3) for high TAFI levels. Annual incidences in subgroups of carriers were 0.35% (0.09-0.89), 0.44% (0.05-1.57) and 0.94% (0.35-2.05) for concomitance of high levels of factor VIII:C, TAFI and both, respectively, as compared to 0.09% (0.00-0.48) in single factor V Leiden carriers and 1.11% (0.30-2.82) for other concomitant disorders. INTERPRETATION AND CONCLUSIONS: High levels of factor VIII:C and TAFI, in contrast with factor XI:C and Lp(a), are mild risk factors for venous thromboembolism, and substantially contribute to the risk of venous thromboembolism in factor V Leiden carriers. Our data support the hypothesis that the clinical expression of factor V Leiden depends on co-segregation of thrombophilic disorders.     

Venous thromboembolism at a young age in a brother and sister with coinheritance of homozygous 20210A/A prothrombin mutation and heterozygous 1691G/A factor V Leiden mutation.

We report on members of a Turkish thrombophilic family with coinheritance of the prothrombin mutation PT20210A and the factor V Leiden mutation. The 23-year-old propositus and his elder sister both had episodes of venous theomboembolism at a young age (23 years and 26 years, respectively) and are homozygous for the PT20210A mutation and heterozygous for the factor V Leiden mutation. The 51-year-old father is suffering from coronary heart disease and is heterozygous for both thrombophilic mutations. The asymptomatic 43-year-old mother is heterozygous for the PT20210A mutation, but without activated protein C resistance. Two other children, a 20-year-old girl who is homozygous for the PT20210A mutation and a 13-year-old boy who is heterozygous for the PT20210A mutation, are both free from activated protein C resistance and thrombosis. This report provides further evidence for an early onset of thromboembolic disorders in individuals with an homozygous state of the prothrombin variant 20210A/A and coinheritance of another thrombophilic mutation. Consensus guidelines are required for the treatment and prophylaxis of patients and subjects who remain asymptomatic with homozygous or more than one heterozygous genetic defect associated with thrombophilia.     

Factor V Leiden: should all women be screened prior to commencing the contraceptive pill?

It has been evident for over 30 years that combined oral contraceptive pills (OCP) increase the risk of venous thromboembolism. Recently, it has been suggested that there is an interaction between combined OCPs and the factor V Leiden mutation with the result that the relative risk of venous thromboembolism (VTE) is higher than expected in women who have this heritable thrombophilic defect using combined oral contraceptive pills. In Caucasian populations, factor V Leiden is very prevalent, being present in between 3 and 7% of Europeans and white North Americans. The high prevalence of the defect and its apparent interaction with combined oral contraceptive pills has led to the suggestion that all women should be screened for factor V Leiden prior to commencing contraceptive pills. Although the relative risk of VTE is very significantly increased in factor V Leiden positive women using contraceptive pills, the absolute incidence of venous thrombotic events is low and fatal pulmonary embolism is rare. It would be extremely costly to screen all women for the factor V Leiden mutation and unlikely to be deemed cost-effective. Widespread screening would result in 3-7% of women being denied the most effective and acceptable form of contraception and may influence negotiations with life insurers. It is suggested that only selected women, i.e. those with a personal history of previous venous thromboembolism and those with a clear family history of VTE are offered screening for thrombophilic defects.     

FV Leiden mutation and risk of recurrent venous thromboembolism in Serbian population

The absolute rate of recurrence of venous thromboembolism (VTE) is approximately 5% per year. There is a lower rate of recurrence in provoked VTE, and higher in idiopathic one. So far, there is no consensus whether hereditary thrombophilia should be considered as a persistent risk factor, and whether it requires long-term anticoagulant therapy. The aim of our study was to estimate the risk of recurrent VTE in patients carrying FV Leiden mutation in Serbian population.In retrospective study (1994-2006), we have evaluated the risk of recurrent VTE in 56 patients who are carriers of FV Leiden mutation, in comparison to group consisting of 56 patients non-carriers of FV Leiden mutation. Patients with FII G20210A and MTHFR C677T mutations, antiphospholipid antibodies, antithrombin III, protein C or protein S deficiency, malignancies and diabetes were excluded from the study.Recurrent VTE occurred in 44.6% of the patients, carriers of the FV Leiden mutations, vs. 26.7% in non-carriers group (P<0.05). The incidence rate was 3.7 and 2.2% per year, respectively. The estimated relative risk of recurrence for FV Leiden carriers was 1.67 (95% CI 0.99-2.81, P=0.049). The 60% of patients with mutation and only 13% without mutation develop rethrombosis during first year after discontinuance of therapy (P<0.01).In our study patients with symptomatic VTE who are carriers of the FV Leiden gene mutations have a higher risk of recurrent VTE than non-carriers. Our data suggest the importance of the FV Leiden mutation detection and the estimation of the clinical condition for successful secondary prophylaxis of VTE.     

Factor V Leiden in women: a thrombotic risk factor or an evolutionary advantage?

Factor V Leiden is a common gain-of-function gene mutation resulting in a genetic predisposition to thromboembolic complications. Growing evidence in the literature indicates an interaction between factor V Leiden thrombophilia and acquired prothrombotic conditions such as contraceptive use or hormone replacement therapy, resulting in an increased risk of venous thromboembolism (VTE). Similarly, when combined with the prothrombotic influence of pregnancy, women who are carriers of factor V Leiden are faced with an increased risk of adverse pregnancy outcomes, including VTE, pre-eclampsia, fetal loss, placental abruption, and fetal growth restriction. The results of the most important meta-analyses on the relationship between inherited (factor V Leiden) and acquired thrombophilia in women are analyzed in this review, along with the possible evolutionary role of this mutation.     

Primary thrombophilia in Mexico. II. Factor V G1691A (Leiden), prothrombin G20210A, and methylenetetrahydrofolate reductase C677T polymorphism in thrombophilic Mexican mestizos.

We have shown that in Mexican mestizo patients with clinical features of primary thrombophilia, 39% have activated protein C resistance phenotype, 5% protein C deficiency, and 2% protein S deficiency. In the present study, in a group of 37 thrombophilic Mexicans and 50 normal controls, we assessed the factor V G1691A (Leiden), the prothrombin G20210A, and the methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphisms. Four patients were found to be heterozygous for factor V Leiden, 5 heterozygous for the prothrombin 20210, 16 heterozygous, and 6 homozygous for the MTHFR 677. There were four individuals with co-segregation of alleles: two heterozygotes for the factor V Leiden/prothrombin 20210, one heterozygote for prothrombin 20210/MTHFR 677, and one heterozygote for prothrombin 20210/homozygote for MTHFR 677. For factor V Leiden, prothrombin 20210, and MTHFR 677 mutations, the allele frequencies were respectively 1% (+/-0.2%, alpha = 0.05), <1% and 51% (+/-5%, alpha = 0.05), with calculated relative risks for thrombosis of 5.94 (P = 0.08), >7.66 (P < 0.05), and 0.44 (P NS), respectively. In Mexican mestizo thrombophilic patients, the low prevalence of the factor V Leiden mutation (10.8%) and the high prevalence of the prothrombin 20210 mutation (13.5%) contrast with those identified in Caucasian thrombophilic patients (21% and 6%, respectively; P < 0.01). On the other hand, the high prevalence of the MTHFR 677 mutation gene both in normal controls (78%) and thrombophilic patients (61%) does not support a role of this mutation in the thrombogenesis of Mexican mestizo patients.     

Ramifications of four concurrent thrombophilic mutations and one hypofibrinolytic mutation.

A kindred was examined in which the 48-year-old white female proband with three deep venous thrombosis-pulmonary emboli events had four thrombophilic and one hypofibrinolytic mutations, and in which her 14-year-old asymptomatic daughter had four thrombophilic mutations. The proband was heterozygous for the G1691A factor V Leiden, G20210A prothrombin, and platelet glycoprotein IIIa PL A1/A2 mutations, had high factor VIII (221%), and was homozygous for the 4G4G plasminogen activator inhibitor-1 gene mutation, with high plasminogen activator inhibitor activity (23.7 U/mL). Her 14-year-old daughter was homozygous for the G1691A factor V Leiden and platelet glycoprotein IIb-IIIa PL A2/A2 mutations, compound heterozygous for the C677T and A1298C methylenetetrahydrofolate reductase (MTHFR) mutations, and heterozygous for the G20210A prothrombin mutation, a combination with an estimated likelihood of 1.6 x 10(-7). In 247 white healthy controls, there was no V Leiden homozygosity and no V Leiden-prothrombin gene compound heterozygosity. Heterozygosity for the V Leiden and prothrombin gene mutations was 3.2% and 4.1%, respectively. Homozygosity for the platelet glycoprotein IIb-IIIa PL A2A2, PAI-1 gene 4G4G, and C677T MTHFR mutations was 3.2%, 22.7%, and 12%, respectively. The proband will receive anticoagulation therapy for life. Beyond aspirin, avoidance of exogenous estrogens, and enoxaparin prophylaxis during pregnancy, it is not known whether the proband's daughter should have lifelong anticoagulation therapy, or only after her first thrombotic event.