The role of inherited thrombophilia in venous thromboembolism associated with pregnancy

Antenatal predictors of intestinal pathologies in fetal bowel dilatation

AIM

Fetal bowel dilatation (FBD) in the late trimester of pregnancy can be related with varies of prognosis. Our aims were to obtain antenatal factors that might have relevance for the distinct prognosis with FBD.

METHODS

Seven features of 68 pregnancies presented with FBD were assessed. The best cut-off value to predict intestinal outcomes was selected using receiver-operating characteristics curves, and the effective variables were included into a logistic regression model.

RESULTS

The best cut-off valves to predict intestinal pathologies were 14.5 mm of fetus dilated loop and 37.7 weeks of gestational age at delivery, respectively. The congenital gastrointestinal tract anomalies included 24 cases (92.3%) of intestine atresia, 1 case (3.85%) of small intestine volvulus and 1 case (3.85%) of midgut malrotation.

CONCLUSION

Fetal dilated loops and gestational age at delivery are both an independent risk factor for predicting intestinal pathologies of newborns, which should arouse high attention.

Overcoming heparin resistance in pregnant women with antithrombin deficiency: a case report and review of the literature

Background

The risk of thromboembolic events during pregnancy in patients with antithrombin deficiency is increased. Preventing thromboembolic events during pregnancy in the case of antithrombin deficiency is still a matter of concern.

Case presentation

We present a case of a 19-year-old primigravida Greek Pomak woman, who was diagnosed as having congenital antithrombin deficiency. She had a history of recurrent miscarriages and a family history of thrombosis. She was managed with adjusted doses of low molecular weight heparin throughout her pregnancy, with regular anti-Xa and antithrombin level monitoring. Prior to delivery and for 4 days after delivery she received human antithrombin III concentrate. She delivered a small for gestational age baby with no other complications. She required an increased dose of heparin due to heparin resistance.

Conclusions

Antithrombin deficiency is associated with an increased risk of venous thromboembolic events with a 50% risk of thromboembolic events before the 50th year of life. It is a rare condition, so data concerning the optimal management during pregnancy are limited. The selection of patients who should receive low molecular weight heparin prophylaxis as well as dose intensity and monitoring are discussed. In our patient a conventional low molecular weight heparin dose proved to be inadequate at least at the laboratory level.

Clinical 'Pearls' of maternal critical care: part I

PURPOSE OF REVIEW

This review outlines the challenges in looking after pregnant women with thromboembolism and sepsis who either become or are at risk of becoming critically ill during pregnancy.

RECENT FINDINGS

The Pregnancy Mortality Surveillance systems in both the USA and UK record the most common causes of maternal death as thromboembolism and sepsis. Both of these conditions have improved outcomes with timely maternal critical care provided by a multidisciplinary team.

SUMMARY

In this review, we discuss the pathophysiology, diagnosis, and management of thromboembolism and sepsis, two very important conditions with high mortality requiring admission to intensive care.

Venous Thromboembolism in Pregnancy

The risk of venous thromboembolism (VTE) is increased in pregnancy and puerperium. Thrombophilia has been identified in pregnancy-related VTE. Venous ultrasound and ventilation-perfusion lung scanning are the initial tests; pulmonary angiography should be performed if necessary for the definitive diagnosis. Anticoagulation is achieved with heparin antepartum and warfarin postpartum. Low molecular weight heparin has been effective and safe in pregnancy. Thrombolytic therapy has been administered to pregnant patients.

Profilaxia de tromboembolismo venoso na gestação

O tromboembolismo venoso é importante causa de morbidade e mortalidade obstétrica. Durante a gestação, o risco de sua ocorrência aumenta entre cinco e dez vezes quando comparado ao de mulheres não gestantes de mesma idade. Associado a esse fato, a gestante apresenta algumas limitações para o diagnóstico clínico (alta frequência de dor e edema nos membros inferiores), ecográfico (menor sensibilidade e especificidade no diagnóstico de trombose venosa de ilíaca com a evolução da gestação) e laboratorial (o D-dímero apresenta aumento progressivo no decorrer da gravidez). Uma estratificação criteriosa de risco de tromboembolismo venoso de cada mulher antes da gestação pode diminuir a incidência dessa doença, frequente e de difícil diagnóstico na gravidez, e suas complicações.

Pulmonary embolus in pregnancy

Venous thromboembolism remains in the top three leading causes of maternal death in the US, representing 10.2% of pregnancy-related deaths. Risk of developing a pulmonary embolus appears to increase throughout pregnancy, with a peak in incidence in the early postpartum period. Overall the incidence of VTE is 0.6-1.8 VTEs per 1000 deliveries. Diagnosis and management of pulmonary embolus can prove challenging, but the aim should be to optimize maternal outcome while minimizing hemorrhagic complications. Low-molecular-weight heparin is a safe and effective treatment for the majority of cases of pregnancy-related pulmonary embolus.

Inherited thrombophilia and gestational venous thromboembolism

Thromboembolic disease remains a leading cause of maternal mortality during pregnancy and the puerperium. Rational and risk-adapted administration of heparin prophylaxis depends on the identification of those women who have an increased risk of thrombosis and the accurate quantification of this risk. In women without prior thrombosis, the presence of a heterozygous factor V Leiden or heterozygous G20210A mutation in the prothrombin gene is associated with a pregnancy-associated thrombotic risk of approximately 1 in 400. Thus, in pregnant carriers of either one of these mutations, the risk of venous thromboembolism is low. Therefore, no heparin prophylaxis is recommended. A combination of the two genetic risk factors can increase the risk to a modest level of 1 in 25. In all women with prior thrombosis, the authors recommend heparin prophylaxis throughout pregnancy and postpartum for 6 weeks (inconsistent data). However, according to the American College of Chest Physicians recommendations, in the subgroup of women with an episode of prior thrombosis associated with a transient risk factor, such as surgery or trauma, and no additional genetic risk factor, clinical surveillance throughout pregnancy and heparin prophylaxis postpartum is possible. Despite the remarkable progress in risk stratification, the absolute magnitude of risk and the optimum management is, in many cases, an issue of ongoing debate.

The use of a scoring system to guide thromboprophylaxis in a high-risk pregnant population

Guidelines for thromboprophylaxis in pregnancy are usually based upon clinical observations and expert opinion. For optimal impact, their use must be attended by consistency in the advice given to women. In this observational study, we evaluated the performance of a scoring system, used as a guide for clinicians administering dalteparin to pregnant women at increased risk of venous thromboembolism. The work included 47 women treated with dalteparin prior to adoption of the scoring system and 58 women treated with dalteparin after its adoption. The indication for thromboprophylaxis was recorded in each case together with details of the regimen employed, obstetric, and haematological outcomes. The main outcome measure was to determine whether consistency improved after adoption of the scoring system. We also recorded the occurrence of any new venous thromboembolism, haemorrhage, the use of regional anaesthesia during labour, evidence of allergy, and thrombocytopenia. We found that use of the scoring system improved the consistency of advice and increased the mean duration of thromboprophylaxis. None of the subjects suffered venous thromboembolism after assessment using the scoring system. There was no increase in obstetric or anaesthetic morbidity when dalteparin was given antenatally period and no evidence of heparin-induced thrombocytopenia.

A retrospective study of the factors associated with hypercoagulability in the pediatric patients at a tertiary care children's hospital

OBJECTIVE

The objective of this study was to determine the risk factors of hypercoagulability in children. We explored the interaction of multiple risk factors with the incidence of thrombosis. Our hypothesis was that as the number of risk factors for thrombosis increased the actual incidence of thrombosis would also increase.

DESIGN

Retrospective review from 2003 through 2006 based on a search using two electronic medical record databases.

SETTING

Pediatric Tertiary Care Children's Hospital.

PATIENTS

Two hundred twenty-six patients were identified and analyzed.

MEASUREMENTS

Search terms included factor V Leiden polymerase chain reaction, prothrombin gene 20210A mutation, methylene tetrahydrofolate reductase mutation, antithrombin III, and protein C and S levels. Clinical data were compiled for regression analysis.

MAIN RESULTS

The presence of one risk factor was not significant. Two risk factors increased the risk of thrombosis (p = 0.005; OR 3.128). Three or more risk factors further increased the risk of thrombosis (p = 0.003; OR 4.861). Older age (>11 yrs) was protective against thrombosis (p = 0.007; OR 0.995), and the presence of a central venous catheter when analyzed against accumulating risk factors showed a higher risk than that found during the regression analysis (p = 0.001; OR 3.638).

CONCLUSIONS

The population at our institution is reflective of the previously reported standards for the genetic predispositions toward thrombosis. Although older age is associated with a lower incidence of thrombosis, the presence of a central venous access device is detrimental. Accumulation of factors results in an increased risk of thrombosis. This article suggests that when inserting a central venous access device, consideration of a hypercoagulation workup should occur. Those with any two or more risk factors, genetic or acquired, and the comorbidity of a CVL may warrant consideration for the institution of anticoagulation with an agent like low molecular weight heparin.

Antithrombotic therapy and pregnancy: consensus report and recommendations for prevention and treatment of venous thromboembolism and adverse pregnancy outcomes

Venous thromboembolism and adverse pregnancy outcomes are potential complications of pregnancy. Numerous studies have evaluated both the risk factors for and the prevention and management of these outcomes in pregnant patients. This consensus group was convened to provide concise recommendations, based on the currently available literature, regarding the use of antithrombotic therapy in pregnant patients at risk for venous thromboembolic events and adverse pregnancy outcomes.

Placental histopathologic features in patients with thrombophilic mutations

The purpose of this article is to review the histopathologic findings in the placenta of women with a known thrombophilic mutation. The findings range from normal to severe pathologic features including decidual vasculopathy, placental infarctions, syncytial knotting, maternal floor infarction, fetal thrombotic vasculopathy, vasculitis, and chronic villitis. They are, however, not pathognomonic of thrombophilic states, nor are necessarily markers of perinatal damage. The prospective evaluation of cases with known thrombophilic mutations and the application of tissue microarray examination of the placenta may allow identification of major histopathologic features and molecular parameters associated with maternal and/or fetal thrombophilic states. This may assist clinicians in their consultation with patients and optimize management in future pregnancies.

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

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

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.

Haemostasis in normal pregnancy: a balancing act?

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

Low-molecular-weight heparin for the prevention and treatment of venous thromboembolism in pregnancy

PURPOSE OF REVIEW

Low-molecular-weight heparins (LMWHs) have largely replaced unfractionated heparins for both prophylaxis and treatment of venous thromboembolism in nonpregnant patients. However, until recently, evidence in pregnant women was lacking, despite the increasing use of LMWHs during pregnancy in clinical practice. This review covers recent literature on the use of LMWHs in relation to pregnancy.

RECENT FINDINGS

The main areas covered in this review are the use of LMWHs in both prophylaxis and treatment of venous thromboembolism in pregnancy. The review also considers issues relating to monitoring of LMWHs in pregnancy, and safety from both a maternal and a fetal perspective.

SUMMARY

The available evidence demonstrates that LMWHs are of at least equivalent efficacy but have a better safety profile compared with unfractionated heparins in both prophylaxis and treatment of maternal venous thromboembolism, and are more convenient to administer. There is no consensus with respect to whether these agents require monitoring during pregnancy other than periodic checking of the platelet count. The clinical implication from the available evidence is that LMWHs should now be regarded as the anticoagulant agents of choice for both prophylaxis and treatment of maternal venous thromboembolism.

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.

Tinzaparin sodium for thrombosis treatment and prevention during pregnancy

OBJECTIVE

This study was undertaken to assess the pharmacodynamic profile, safety, and efficacy of tinzaparin during pregnancy.

STUDY DESIGN

Fifty-four pregnant women, 12 for treatment of thrombosis and 42 for thromboprophylaxis, received tinzaparin by once daily injection. Four-hour postdose anti-Xa results were analyzed by use of repeated measures statistical methods.

RESULTS

One woman (3.4%) on the 175 anti-Xa U/kg dose and three women (20%) on the 50 anti-Xa U/kg dose required a dose increase during the initial dose titration phase to achieve target anti-Xa activity. No thrombotic events occurred.

CONCLUSION

The 175 anti-Xa U/kg dose is appropriate for treatment and for high-risk thromboprophylaxis throughout pregnancy. In pregnant women at moderate risk of thrombosis, a higher tinzaparin dose is required than in the nonpregnant state and 75 anti-Xa U/kg appears to be appropriate. The majority of women do not need a dose increase with advancing gestation.

Pregnancy-associated venous thromboembolism (VTE) in combined heterozygous factor V Leiden (FVL) and prothrombin (FII) 20210 A mutation and in heterozygous FII single gene mutation alone

The risk of venous thromboembolism (VTE) in the absence of prophylaxis was evaluated in a retrospective study of 47 women (84 pregnancies) with combined thrombophilia [heterozygous factor V Leiden (FVL) plus prothrombin (FII) 20210A mutation (group I)] and in 82 women (193 pregnancies) with the FII alone (group II). VTE was more frequent in group I than in group II [17.8% versus 6.2%, P = 0.003, relative risk (RR) 2.9, 95% confidence interval (CI) 1.4-5.9], ante partum (7.1% and 2.1%) and post partum (11.5% and 4.2%). The risk was higher in index cases than in family members (RR 2.5, 95% CI 1.2-5.2 and RR 2.1, 95% CI 0.2-22.3 respectively) Even women who had no history of VTE before pregnancy had an increased risk (RR 2.2, 95% CI 1.0-4.8). Our results suggest that, during ante partum, prophylaxis is indicated in women with combined thrombophilia and with a VTE before pregnancy. In those without VTE before pregnancy, prophylaxis might be decided for each individual case, taking into consideration all risk factors. In women with the FII mutation alone, the low risk may not justify prophylaxis in the absence of previous VTE. In post partum, prophylaxis is indicated in all cases.

Risk factors for thrombosis in pregnancy

Pregnancy is a hypercoagulable state affecting both the coagulation and the fibrinolytic systems. Any exacerbation of the pre-disposing factors for coagulation may well lead to a thrombotic event more often in pregnant women than in the general population. Arterial thrombosis is very rare in pregnancy. Pre-eclampsia may be a risk factor for the development of arterial disease in later life. Venous thromboembolism (VTE) in pregnancy, although still rare, is a major cause of maternal mortality. Risk factors, such as older age, increased weight and emergency Caesarean section, as well as acquired and genetic thrombophilia, often coexist and reinforce each other. Appropriate thromboprophylaxis needs to be considered and applied on an individual basis. Uteroplacental thrombosis provides a common pathophysiological link between various poor pregnancy outcomes, including recurrent miscarriage, stillbirth, placental abruption, fetal growth restriction and pre-eclampsia. Its significance depends on the gestational age. Acquired and genetic thrombophilia may be associated with such conditions, particularly in early-onset disease. More data are required to assess the significance of such thrombophilias in obstetric practice. Any treatment should be in the context of clinical trials.

Inherited thrombophilia and gestational venous thromboembolism

Thromboembolic disease is a leading cause of maternal morbidity and mortality during pregnancy and the puerperium. To reduce the incidence of venous thromboembolism in pregnancy and improve outcomes, an individual risk stratification based on probability of thrombosis as a rationale for an individual risk-adapted prophylaxis is required. Within the past 10 years, a significant improvement in risk estimation has been achieved due to the identification of new genetic risk factors of thrombosis. In women without prior thrombosis, the presence of a heterozygous factor V Leiden or heterozygous G20210A mutation in the prothrombin gene is associated with a pregnancy-associated thrombotic risk of approximately 1 in 400. Thus, in pregnant carriers of either one of these mutations the risk of venous thromboembolism is low--indicating that pregnancy-associated thrombosis is multicausal, resulting from the interaction of combined defects. A combination of the two genetic risk factors can increase the risk to a modest level (risk 1 in 25). In women with a single episode of prior thrombosis associated with a transient risk factor, for example, surgery or trauma, and no additional genetic risk factor, the probability of a pregnancy-associated thrombosis appears also to be low. In contrast, in women with a prior idiopathic venous thrombosis who carry an additional hereditary risk factor or who have a positive family history of thrombosis, a high risk (>10%) can be expected, supporting the indication for active antepartum and postpartum heparin prophylaxis. Despite the remarkable progress in risk stratification, the absolute magnitude of risk in many cases is unknown and current recommendations remain empirical.

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.

Inherited thrombophilia and stillbirth

Thrombophilias are inherited or acquired conditions that predispose individuals to thromboembolism. New inherited thrombophilias are recognized each year. Some, but not all, studies have found an association between inherited thrombophilias and adverse pregnancy outcomes, including fetal loss. The controversy regarding the clinical implications of thrombophilias in pregnancy is clouded by differences in study populations, the number of thrombophilias tested, interactions between thrombophilias, and the retrospective nature of most studies, just to name a few factors. The lack of adequately designed studies also extends to clinical management. Clear evidence to determine when to test, whom to test, which thrombophilias to test for, when to treat, and what to treat with is not available. Further studies to investigate these questions are urgently needed.

Hazards of assisted conception in women with severe medical disease

The issues relating to assisted reproduction in women with severe medical disease can be divided into the likely effect of pregnancy upon the medical condition, and how the medical condition may adversely affect pregnancy outcome. In addition, consideration of the hazards relating to the process of assisted conception, in particular the risk of ovarian hyperstimulation syndrome and multiple pregnancy, must be remembered. In some women, successful assisted reproduction may result in a life-threatening pregnancy. Clinicians advising women about assisted conception should be aware of the medical conditions that are absolute contra-indications to pregnancy. Some women with severe medical disease may have a significantly reduced life expectancy, in which case ethical issues regarding the future welfare of the child must be considered. Examples include sickle cell disease, cystic fibrosis and HIV. One of the biggest advantages of assisted reproduction for women with severe medical disorders is that the pregnancy is planned. Thus, there is an opportunity for the patient to be informed fully about any risks, both to herself and her fetus. This article reviews the general management of women with severe medical disorders who seek assisted reproduction and gives specific guidelines for the more common conditions.

Medical and obstetric problems complicating pregnancy

The present review addresses several medical and obstetric factors/problems, and their interactions during pregnancy. These include the following: maternal age; morbidity and mortality during pregnancy; thromboembolism; gestational diabetes; haemolysis, elevated liver enzymes, low platelets syndrome; human immunodeficiency virus; hepatitis C; preterm labour; antenatal administration of corticosteroids; intrapartum surveillance; breech delivery; and caesarean section.

Management of heparin allergy during pregnancy with danaparoid

We report a patient who presented with a left proximal deep vein thrombosis at 25 + 5 weeks gestation. She developed a severe urticarial rash 3 weeks following initiation of therapy with Enoxaparin. The patient was heterozygous for the factor V Leiden mutation. She was treated with subcutaneous twice-daily danaparoid (Orgaran) for the remainder of the pregnancy, achieving anti-Xa levels in the therapeutic range 0.5-1.0 IU/ml. Delivery was at term by caesarean section 2 days after spontaneous rupture of membranes and failure to progress in labour. Danaparoid was withheld during this time. Danaparoid was restarted 3 h post delivery and the patient anticoagulated with warfarin in the post-partum period. There was no recurrence of thrombosis or bleeding events during therapy with danaparoid. No anti-Xa activity was demonstrated in breast milk.

Low-molecular-weight heparin during pregnancy

Thromboembolism is an infrequent, yet serious cause of both maternal and fetal morbidity and death during pregnancy and the puerperium. Pregnancy itself increases the risk of thromboembolic complications probably owing to a combination of hypercoagulability and venous stasis due to venous dilation. Recent studies have indicated that some serious obstetric complications are correlated with inherited or acquired thrombophilia. The prevalence of venous thromboembolism (VTE) has been extimated to be 1 per 1000-2000 pregnancies in retrospective studies. Anticoagulant treatment and prophylaxis both before and during pregnancy are based on unfractionated heparin (UH), low-molecular-weight heparin (LMWH) and warfarin. Warfarin is teratogenous if administered between the 6th and the 12th week. LMWH is replacing UH in the prevention and treatment of VTE both outside and more recently during pregnancy with the same indications, and also for obstetric complications. This paper assesses the safety and efficacy of heparin therapy during pregnancy and the puerperium. Its cardiovascular and obstetric indications and regimens and maternal and fetal side-effects are also discussed.

Use of antithrombotic agents during pregnancy

Anticoagulant therapy is indicated during pregnancy for the prevention and treatment of VTE; for the prevention and treatment of systemic embolism in patients with mechanical heart valves; and, often in combination with aspirin, for the prevention of pregnancy loss in women with APLAs or thrombophilia and previous pregnancy losses. Several questions concerning anticoagulant therapy remain unanswered. It appears that LMWH will largely replace UFH. Oral anticoagulants are fetopathic, but the true risks of the warfarin embryopathy and CNS abnormalities remain unknown. There is considerable evidence that warfarin embryopathy occurs only when oral anticoagulants are administered between the sixth week and the 12th week of gestation and that oral anticoagulants may not be fetopathic when administered in the first 6 weeks of gestation. Oral anticoagulant therapy should be avoided in the weeks before delivery because of the risk of serious perinatal bleeding caused by the trauma of delivery to the anticoagulated fetus. The safety of aspirin during the first trimester of pregnancy is still a subject of debate. There is a concern about the efficacy of UFH in the prevention of arterial embolism in pregnant women with mechanical heart valves. Finally, the optimum management of pregnant women with thrombophilia (and prior pregnancy loss and/or prior VTE) is unknown, but trials of anticoagulant therapy are ongoing. Because it is safe for the fetus, LMWH (or UFH) is the anticoagulant of choice during pregnancy for situations in which its efficacy is established. There is some doubt that heparin is effective for the prevention of systemic embolism in patients with mechanical heart valves. Low doses of heparin or poorly controlled heparin therapy are not effective in preventing systemic embolism in patients with mechanical heart valves.

Prothrombin 20210 G-->A, MTHFR C677T mutations in women with venous thromboembolism associated with pregnancy

Over 50 unselected women with maternal venous thromboembolism were screened for the prothrombin 20210 G-->A and MTHFR C677T mutations, in addition to screening for other thrombophilias. The prevalence of thrombophilia in these women was compared with its prevalence in the general population in our area. The prothrombin (OR 4.4; 95% CI 1.2-16) and factor V Leiden (OR 4.5; 95% CI 2.1-14.5) mutations were more common in our patients, compared with the general population, whereas women homozygous for the C677T mutation in the methylene tetrahydrofolate reductase gene (OR 0.45; 95% CI 0.13-1.58) were not. It is recommended that women with a personal or strong family history of venous thromboembolism should be screened for the prothrombin mutation either before or early in pregnancy, in addition to screening for other thrombophilias. Screening for the MTHFR mutation does not appear to identify women at increased risk of maternal venous thrombosis.

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.