Inherited thrombophilias and adverse pregnancy outcome: screening and management

Inherited thrombophilias are a heterogenous group of conditions which have been implicated in a variety of pregnancy complications. Evidence is mounting that implicates these inherited disorders in a range of pregnancy outcomes, including recurrent miscarriage, late fetal loss, preeclampsia, abruptio placentae, and intrauterine growth restriction. The most commonly identified inherited thrombophilias consist of Factor V Leiden and the prothrombin gene mutation G20210A. Rarer inherited thrombophilic conditions include deficiencies of protein S, C and antithrombin. More recently, deficiency of protein Z has been linked to pregnancy complications, including preterm delivery. Clinical manifestations often are associated with the presence of more than one inherited thrombophilia, consistent with their multigenic nature. Some, but not all, studies investigating the use of heparin to prevent adverse pregnancy outcome have demonstrated a benefit. However, an adequate randomized trial is required to definitively determine whether heparin anticoagulation is the best prevention option in patients who harbor one or more inherited thrombophilias and are at risk for adverse pregnancy outcome. This review will summarize the association of thrombophilic conditions and obstetrical complications.     

Thromboembolic disease in pregnancy

Recent publications have produced some new estimates of the incidence of pregnancy-related venous thromboembolic disease, and have found increasing evidence of an association between inherited thrombophilias and pregnancy complications and fetal loss. The balance of benefit and risk of thromboprophylaxis remains to be evaluated, and studies are needed to provide a sound basis for clinical practice.     

Thrombophilias and recurrent miscarriage

Inherited and acquired thrombophilias have been associated with recurrent pregnancy loss. Over recent years our ability to detect protein and genetic abnormalities responsible for thrombotic tendency has improved. We are now left with the task of deciphering which of these thrombophilias carries an increased risk for recurrent pregnancy loss. Acquired thrombophilias including lupus anticoagulant and anticardiolipin antibodies have been linked to recurrent pregnancy loss. However the evidence for the role of inherited thrombophilias such as, heterozygosity for the factor V Leiden, prothrombin G20210A mutation, the methylenetetrahydrofolate reductase (C677T MTHFR) mutation, as well as deficiencies of antithrombin, protein C and protein S is less clear. The methods for diagnosis and the evidence for their associations are discussed in this paper. Treatment modalities independent of those needed to prevent thrombotic events in pregnancy have generally not been studied. Given the present available data, there is insufficient evidence to include inherited thrombophilias in the initial evaluation of RPL. It is important to look for other, more common, causes of recurrent miscarriage in the evaluation of these patients.     

Preconception counseling for women with thrombophilia

Inherited thrombophilias are a heterogeneous group of coagulation disorders that predispose individuals to thromboembolic events. This group of conditions is the major risk factor for thromboembolism during pregnancy and the puerperium. In addition, thrombophilias have been associated with several adverse obstetric events, including pregnancy loss, preeclampsia, placental abruption, and intrauterine growth restriction. An increased risk for these obstetric complications has prompted many authorities to recommend screening and treating pregnant women for thrombophilias. Optimal obstetric management, however, is controversial as thrombophilias are common and many affected individuals are asymptomatic. Indeed, pregnancy outcome in most women with thrombophilias is normal. The most commonly identified inherited thrombophilias are the factor V Leiden and prothrombin G20210A gene mutations. More rare thrombophilias include protein C and S deficiencies, antithrombin III deficiency. Although relatively common, the association between hyperhomocysteinemia and associated mutations (such as the C677 T methylenetetrahydro-folate reductase) and obstetric complications is controversial.     

Acquired and inherited thrombophilia disorders in pregnancy

Thromboembolism is the leading cause of antepartum and postpartum maternal mortality. The presence of antiphospholipid antibodies is responsible for many pregnancy losses and other morbidities in pregnant women, and is the most prevalent and treatable cause of acquired thrombophilia in pregnancy. There is also evidence that women with thrombophilia are at increased risk not only of pregnancy-related venous thromboembolism but other vascular pregnancy complications. Many studies have examined the association between thrombophilia and pregnancy complications. This article reviews the most up-to-date knowledge of prevalence, pathogenesis, and diagnosis of acquired and inherited thrombophilias and their relationship and association with pregnancy complications.     

遗传性易栓症的妊娠期筛查与抗凝治疗评价

汉族人群遗传性易栓症以蛋白C或蛋白S缺乏为主,抗凝血酶缺乏少见,罕见凝血因子ⅤLeiden(FⅤL)突变及PGM突变。遗传性易栓症增加妊娠期血栓栓塞性疾病的风险,是胎盘介导的妊娠并发症的协同性促进因素,而不是主要病因。如果已经明确具有进行治疗的指征,没有必要再行遗传性易栓症的筛查;如果病因不明,而遗传性易栓症筛查的阳性结果可能会影响治疗决策时,筛查或许是有用的。现有证据仅表明,预防性应用低剂量阿司匹林可以减少子痫前期复发。低分子肝素是否能改善胎盘介导的妊娠并发症的再发风险,单中心和多中心研究的结论并不一致。虽然缺乏有力的证据支持,目前仍建议对具有胎盘介导的妊娠并发症病史的遗传性易栓症患者进行选择性、个体化抗凝治疗。     

Inherited thrombophilias

Many inherited thrombophilias have been detected and the pathophysiologic insight has increased tremendously during the last decades. Despite, however, the overwhelming observational evidence on the association between inherited thrombophilia and several women's health issues, including VTE, thus far the implications for clinical practice are uncertain. Although there is firm epidemiologic evidence that is helpful in counseling women who have inherited thrombophilia to prevent a first or recurrent VTE, the uncertainty is particularly present for women who have other pregnancy complications, such as recurrent pregnancy loss and pre-eclampsia. For this group, well-designed placebo-controlled trials to assess the harm-benefit ratio are urgently needed.     

Second-trimester maternal serum alpha-fetoprotein (MSAFP) is elevated in women with adverse pregnancy outcome associated with inherited thrombophilias

Obstetric complications, such as severe pre-eclampsia, fetal growth restriction, abruptio placentae, or stillbirth are associated with abnormally elevated second-trimester maternal serum alpha-fetoprotein (MSAFP) and beta subunit of human chorionic gonadotrophin (betahCG). This has been attributed to placental abnormalities. Women with thrombophilias have been shown to have abnormalities of the placenta resulting in adverse pregnancy outcome in these patients. The purpose of the present study was to evaluate whether women with pregnancy complications and inherited thrombophilias have abnormally elevated second-trimester MSAFP or betahCG. Sixty-two women with pregnancy complications were tested for inherited thrombophilias several months after delivery. The thrombophilia group included 29 women with pregnancy complications and an inherited thrombophilia and the control group included 33 other patients without thrombophilia. Patients in the thrombophilia group had a higher median MoM MSAFP compared to the controls (1.337 vs. 1.086, p=0.0516). The incidence of abnormally elevated MSAFP (>2.5 MoM) was also significantly higher in the thrombophilia group compared to controls (21% vs. 3%, p=0.04). Neither the median MoM betahCG nor the incidence of abnormally elevated betahCG were significantly different between the groups. We conclude that second trimester MSAFP, but not betahCG, is abnormally elevated in patients with thrombophilia and obstetric complications.     

Inherited thrombophilia in pregnancy: a systematic review

The purpose of this study was to conduct a systematic review of the literature of studies that examined the association between inherited thrombophilias and adverse pregnancy outcomes. We have evaluated developments in this area published since 1998. The published studies differ widely in design, mostly in patients and controls selection and in data analytic approach. Despite the growing evidence in the literature, there are still gaps in our knowledge of thrombophilia in pregnancy, specially regarding less prevalent thrombophilic defects, such as deficiencies in antithrombin, protein C, and S. Several studies on the association on factor V Leiden showed that it may play a role not only in second trimester losses, but also in pre-eclampsia, intrauterine growth-retardation, and placental abruption. Studies on the prothrombin gene mutation yielded conflicting results. Further large prospective studies are needed to asses the relative clinical and cost effectiveness of anticoagulant therapies in the prevention of pregnancy adverse outcomes.     

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.     

Recurrent miscarriage: pathophysiology and outcome

PURPOSE OF REVIEW: This article reviews new concepts in the aetiology of recurrent miscarriage, presents new outcome data and evaluates new modalities of treatment for unexplained recurrent miscarriage. RECENT FINDINGS: Preimplantation genetic diagnosis has been considered an option for couples who have structural chromosomal abnormalities or unexplained recurrent miscarriage. The association between thrombophilias and adverse pregnancy outcome is further reviewed. In relation to this, there is increasing support for the use of thromboprophylaxis in improving pregnancy outcome in women with inherited thrombophilias. Nonrandomized studies have shown that the reduction in insulin levels with metformin in insulin-resistant individuals may reduce miscarriage risk by restoring normal haemostasis and improving the endometrial milieu. With respect to immunological concepts there is now evidence to suggest that, in addition to a suppression of maternal cell-mediated immunity, some elements of the innate immune system are activated in successful pregnancies. SUMMARY: With the exception of aspirin and heparin for the prevention of recurrent miscarriage in women with the antiphospholipid syndrome, no other suggested therapies for this heterogeneous group of patients have been evaluated in randomized controlled trials. These include thromboprophylaxis for inherited thrombophilias and use of insulin sensitizers in women with insulin resistance and/or polycystic ovarian syndrome. The role of the innate immune system in pregnancy was recently highlighted, and use of nonspecific therapies to suppress the maternal immune response to pregnancy should be reassessed.     

Thrombophilias, perinatal stroke, and cerebral palsy

Perinatal ischemic stroke has become recognized as a not-rare adverse outcome of pregnancy and a common cause of chronic neurologic disability in children. This review discusses the clinical entity, perinatal stroke, and its relationship to thrombophilias, inherited and acquired, and to maternal and pregnancy factors.     

Haemostasis in normal and abnormal pregnancy

Haemostasis is a complex and dynamic equilibrium involving pro-coagulants, the natural anticoagulation system and fibrinolysis. Normal human pregnancy is associated with profound alterations to the process of haemostasis such that the pro-coagulant effect becomes dominant. There are very few studies which have attempted to elucidate the adaptations that take place in the uteroplacental circulation where the haemostatic system faces the conflicting tasks of maintaining blood fluidity during pregnancy while preparing for the haemostatic challenge of delivery. It is hypothesised that excessive thrombosis within the uteroplacental circulation provides the mechanistic basis for the reported associations between the inherited thrombophilias and major pregnancy complications. The evidence underpinning this widely quoted hypothesis is weak.     

The utility of thrombophilia testing in pregnant women with thrombosis: fact or fiction?

Women who either present with an episode of acute venous thrombosis in pregnancy or who have a history of venous thrombosis who present for prenatal care often undergo testing for inherited thrombophilia. The rationale for screening may include questions about whether screening for inherited thrombophilias can help to alter anticoagulation plans in a pregnancy complicated by venous thrombosis, whether patients with a history of venous thrombosis who present for care in a subsequent pregnancy require anticoagulation and at what intensity, whether knowledge of thrombophilia changes the duration and intensity of anticoagulation outside pregnancy, and whether screening of family members is warranted. Data regarding these issues are reviewed, controversies surrounding thrombophilia testing in this setting are discussed, and clinical recommendations are made.     

Testing for inherited thrombophilia in recurrent miscarriage

Approximately 1-5% of women trying to conceive experience recurrent miscarriage, and in 50% of these women, the cause of the preceding miscarriages is unknown. Inherited thrombophilias such as factor V Leiden mutation, prothrombin gene mutation (PT 20210A), and deficiencies of natural anticoagulants protein C, protein S, and antithrombin are associated with recurrent miscarriage. Knowledge of the association between inherited thrombophilia and recurrent miscarriage and of potential treatment options for improving chances of a live birth could tempt physicians to test for inherited thrombophilia in women with recurrent miscarriage. However, the strength of the association between inherited thrombophilia and recurrent miscarriage is not very strong, and more importantly, no evidence indicates that the use of anticoagulants improves the chance of live birth in these women. With the current state of evidence, testing for inherited thrombophilia should not lead to altered clinical management and therefore, should not be performed routinely in women with recurrent miscarriage but only in the context of scientific studies.     

How strong is the association between maternal thrombophilia and adverse pregnancy outcome? A systematic review.

OBJECTIVE: To determine whether inherited and acquired thrombophilias are associated with adverse obstetric complications. STUDY DESIGN: A systematic review; studies where women with adverse obstetric complications were tested for one or more acquired and inherited thrombophilias were included. MAIN OUTCOME MEASURES: Prevalence of thrombophilia in women with severe pre-eclampsia/eclampsia, severe placental abruption, intrauterine growth restriction or unexplained stillbirth. RESULTS: Compared with controls, placental abruption was more often associated with homozygous and heterozygous factor V Leiden mutation, heterozygous G20210A prothrombin gene mutation, homocysteinaemia, activated protein C resistance or anticardiolipin IgG antibodies. Women with pre-eclampsia/eclampsia were more likely to have heterozygous factor V Leiden mutation, heterozygous G20210A prothrombin gene mutation, homozygous MTHFR C677T mutation, protein C deficiency, protein S deficiency or activated protein C resistance compared with controls. Unexplained stillbirth, when compared with controls, was more often associated with heterozygous factor V Leiden mutation, protein S deficiency, activated protein C resistance, anticardiolipin IgG antibodies or lupus anticoagulant. Women with intrauterine growth restriction had a higher prevalence of heterozygous G20210A prothrombin gene mutation, homozygous MTHFR C677T gene mutation, protein S deficiency or anticardiolipin IgG antibodies than controls. There was wide heterogeneity in the prevalence of thrombophilia between the studies. CONCLUSIONS: Women with adverse pregnancy outcome are more likely to have a positive thrombophilia screen but studies published so far are too small to adequately assess the true size of this association. Screening for thrombophilia should not become standard practice until clear evidence emerges that thromboprophylaxis during pregnancy improves perinatal outcome. Further research into the link between the observed association, causality and heterogeneity is required.     

Thrombophilia and the obstetric patient

OBJECTIVE: To examine how practicing obstetricians evaluate and manage thrombophilias in selected clinical situations. METHODS: A questionnaire investigating knowledge and practice patterns pertaining to thrombophilia was mailed to 300 randomly selected American College of Obstetricians and Gynecologists Fellows and Junior Fellows in February 2005. RESULTS: Approximately 50% (151) of questionnaires were returned. Statistical analysis focused on the 104 responding obstetricians. The majority (greater than 70%) know which thrombophilias are inherited and which are acquired. More than 50% send an inherited thrombophilia panel and antiphospholipid antibodies on patients with a history of fetal demise, intrauterine growth restriction (less than 5th percentile), abruption, and severe preeclampsia. Ninety-two percent test patients with recurrent miscarriages for antiphospholipid antibodies. Despite no clear evidence, 80% also test these patients for inherited thrombophilias. The majority intervene with either thromboprophylaxis or low-dose aspirin when managing patients at risk for thromboembolism. Seventy percent use low-molecular-weight (fractionated) heparin for patients requiring therapeutic anticoagulation, while 62% also use it for prophylactic anticoagulation. Thirty-eight percent of physicians using low-molecular-weight (fractionated) heparin monitor anti-factor Xa levels. The majority (56%) felt their residency training with regard to thrombophilia was barely adequate. Only 8% felt their training was comprehensive, while 36% felt it was adequate. CONCLUSION: Most responding obstetricians do not manage thrombophilia patients according to expert opinion. Despite the fact that often there is no clear evidence for treatment, many physicians are inclined to intervene in patients at risk for thromboembolism. Educational endeavors are needed to guide obstetricians caring for patients at risk for thromboembolism. LEVEL OF EVIDENCE: III.     

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.     

Thromboembolism and thrombophilia in pregnancy

Venous thromboembolism (VTE) is one of the leading causes of maternal mortality worldwide and is also the cause of significant maternal morbidity. This article discusses the risk factors for VTE in pregnancy, the management of the pregnant woman at risk both antenatally and postpartum and the acute management of VTE when it occurs during pregnancy.The thrombophilias, both heritable and acquired are becoming increasingly recognised as a cause of morbidity and mortality both within and outside pregnancy. There has been recent increased interest in the thrombophilias and their link with recurrent miscarriage, pre-eclampsia, abruption and intrauterine growth restriction. The relationship between the thrombophilias and adverse pregnancy outcome is addressed in detail with reference to the current literature available on this evolving subject.     

Inherited thrombophilias in pregnant patients: detection and treatment paradigm

Inherited thrombophilias are the leading cause of maternal thromboembolism and are associated with an increased risk of certain adverse pregnancy outcomes including second- and third-trimester fetal loss, abruptions, severe intrauterine growth restriction, and early-onset, severe preeclampsia. Current information suggests that all patients with a history of prior venous thrombotic events and those with these characteristic adverse pregnancy events should be evaluated for thrombophilias. The most common, clinically significant, inherited thrombophilias are heterozygosity for the factor V Leiden and prothrombin G20210A mutations. The autosomal-dominant deficiencies of protein C and protein S are of comparable thrombogenic potential but are far less common. Homozygosity for the 4G/4G mutation in the type-1 plasminogen activator inhibitor gene and the thermolabile variant of the methylenetetrahydrofolate reductase gene, the leading cause of hyperhomocysteinemia, although relatively common, confer a low risk of thrombosis. In contrast, autosomal-dominant antithrombin deficiency and homozygosity or compound heterozygosity (ie, carriers of one copy of each mutant allele) for the factor V and prothrombin mutations are very rare but highly thrombogenic states. Regardless of their antecedent histories, pregnant patients with these highly thrombogenic conditions are at very high risk for both thromboembolism and characteristic adverse pregnancy outcomes, require full therapeutic heparin therapy throughout pregnancy, and need at least 6 weeks of postpartum oral anticoagulation. There is also compelling evidence that patients with the less thrombogenic thrombophilias and a history of venous thrombotic events or characteristic adverse pregnancy outcomes require prophylactic anticoagulant therapy during pregnancy and, in the case of prior thromboembolism, during the puerperium. Antepartum anticoagulation does not appear warranted among patients with less thrombogenic thrombophilias who are without a history of venous thromboembolism, characteristic adverse pregnancy outcomes, or other high risk factors for venous thrombosis.