Enoxaparin treatment in women with mechanical heart valves during pregnancy

The Safety and Efficacy of Low-Molecular-Weight Heparin in Pregnant Women With Rheumatic Heart Disease and Valves Replacement

Background: In patients with rheumatic heart disease (RHD) and prosthetic valve replacement, the risk of thromboembolic complications is the highest during and immediately after pregnancy. Therapeutic anticoagulation during this period is crucial to minimize the risk of thromboembolic complications. The use of low-molecular-weight heparin (LMWH) remains an off-label indication. The type of anticoagulants used, dosing regimens, target anti-Xa levels, and frequency of anti-Xa monitoring are highly variable in the pregnant population and have been derived from pilots, observational studies, and empirical evidence. Herein, in a real-world setting, we sought to examine the efficacy and safety of variable anticoagulation options with a focus on LMWH in the management of RHD-related valvular disease in pregnant women.

Methods: This study is a retrospective study conducted at a large university-affiliated tertiary care center (King Saud University Medical City) between January 2011 and February 2020. All pregnant women with RHD who had heart valve replacements were reviewed. Patient data were extracted for demographic information, baseline characteristics, anticoagulation type, and primary outcomes. Primary endpoints were thromboembolic events, hemorrhagic complications, and fetal outcomes.

Results: A total of 744 pregnancies in 149 women were identified. The mean age ± SD of the women was 43.8 ± 12 years. A total of 86 women (58%) were on the LMWH regimen, 35 women (23%) were on LMWH and warfarin regimen, and 28 women (19%) were on unfractionated heparin (UFH) and warfarin regimen. Overall, thromboembolic events developed in five (0.7%) pregnancies. Of those, two were in the LMWH group, two were in the LMWH and warfarin group, and one was in the UFH and warfarin group. In addition, significant hemorrhagic complications occurred in five pregnancies. Of these, two occurred in the LMWH group, two in the LMWH and warfarin group, and one in the UFH and warfarin group. No adverse maternal and fetal outcomes were noted.

Conclusion: This study presents the largest retrospective study of variable anticoagulation options in pregnant women with RHD and prosthetic valve replacement. LMWH is both safe and effective in preventing major thromboembolic complications compared to other forms of anticoagulation used during pregnancy.

Anti-Xa Monitoring of Low-Molecular-Weight Heparin during Pregnancy: A Systematic Review

Low-molecular-weight heparin (LMWH) is commonly used for preventing or treating venous thromboembolic disease (VTE) during pregnancy. The physiological changes in maternal metabolism have led to discussions on optimal LMWH dosing strategy and possible need for monitoring. The aim of this systematic review is to summarize and discuss whether LMWH dose adjustment according to anti-Xa provides superior effectiveness and safety compared with weight adjusted or fixed dosed LMWH in pregnant women. A systematic literature search was performed in PubMed, Embase, and Scopus on September 26, 2020. The study is reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Effectiveness was defined as episodes of thrombosis and safety as bleeding episodes. In total, 33 studies were included: 4 randomized controlled studies and 29 cohort studies. Prophylactic dosing strategies employing weight dosed, fixed dosed, or anti-Xa adjusted LMWH dosing performed equal in effectiveness and safety. In pregnant women with VTE or high thromboembolic risk, therapeutic weight-adjusted LMWH and weight plus anti-Xa-adjusted LMWH provided equal results in terms of effectiveness and safety. Pregnant women with mechanical heart valves (MHVs) received therapeutic anti-Xa-adjusted LMWH with four out of seven studies presenting mean peak anti-Xa within target ranges. Still, pregnant women with MHV experienced both thrombosis and bleeding with anti-Xa in target. Based on the results of this systematic review, current evidence does not support the need for anti-Xa monitoring when using LMWH as thromboprophylaxis or treatment during pregnancy. Nonetheless, the need for anti-Xa monitoring in pregnant women with MHV may need further scrutiny.

2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

This executive summary of the valvular heart disease guideline provides recommendations for clinicians to diagnose and manage valvular heart disease as well as supporting documentation to encourage their use.

METHODS

A comprehensive literature search was conducted from January 1, 2010, to March 1, 2020, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, Cochrane, Agency for Healthcare Research and Quality Reports, and other selected database relevant to this guideline. Structure: Many recommendations from the earlier valvular heart disease guidelines have been updated with new evidence and provides newer options for diagnosis and treatment of valvular heart disease. This summary includes only the recommendations from the full guideline which focus on diagnostic work-up, the timing and choice of surgical and catheter interventions, and recommendations for medical therapy. The reader is referred to the full guideline for graphical flow charts, text, and tables with additional details about the rationale for and implementation of each recommendation, and the evidence tables detailing the data considered in developing these guidelines.

Anticoagulation in Pregnant Women With Prosthetic Heart Valves

Background: Pregnancy is associated with an increased risk of thrombosis in women with mechanical prosthetic heart valves. Effective anticoagulation is therefore critical in such patients but remains problematic, since oral anticoagulation and both unfractionated and low-molecular-weight heparin may be associated with important fetal and maternal side effects.

Purpose: To review information related to the use of anticoagulation with both warfarin and heparin and reassess the safety and efficacy of these therapies in pregnant women with mechanical prosthetic heart valves.

Data source and selection: A MEDLINE search from 1966 to October 2003 for English and non-English language articles that reported the use of anticoagulation in pregnancy was conducted. Articles were included if they reported use of anticoagulation in pregnancy with emphasis on those that included women with mechanical prosthetic heart valves.

Conclusions: Anticoagulation prophylaxis with both warfarin and heparin (unfractionated heparin and low-molecular-weight heparin) may be associated with important fetal and maternal side effects. Optional regimens for the treatment of low-risk and high-risk patients are proposed to minimize potential complications.

Pregnancy Outcome in Women with Mechanical Prosthetic Heart Valves Treated with Unfractionated Heparin (UFH) or Enoxaparin

OBJECTIVE

This study was carried out to determine the maternal (including thromboembolic and hemorrhagic complications) and fetal outcomes (including miscarriage, stillbirth, baby death, and live birth) in women with mechanical heart valves managed with therapeutic doses of unfractionated heparin (UFH) versus enoxaparin during pregnancy.

METHODS

This is a prospective comparative, nonrandomized study. Pregnant women with mechanical heart valves presenting to high-risk pregnancy unit of Benha University Hospital, Egypt were treated with UFH 15,000 U/12 h versus enoxaparin (Clexane) 1 mg/kg SC/12 h during pregnancy and the results were analyzed.

RESULTS

40 pregnant women were included in the study. In 20 pregnant women, anticoagulation was with UFH, and 20 pregnant women received enoxaparin. One (3 %) thrombotic complication occurred with enoxaparin treatment. Noncompliance or subtherapeutic levels contributed to this outcome in this case. Antenatal hemorrhage occurred in 4 (10 %) and postpartum hemorrhagic complications in 5 (12.5 %) pregnancies. Of the 32 pregnant women who continued after 20 weeks' gestation, 100 % (17/17) of the women taking predominantly UFH had a surviving infant compared with 93 % (14/15) of the women taking primarily enoxaparin (p = 0.25). One intrauterine fetal death occurred in the enoxaparin group. There was no significant difference in the live birth rates between the two groups (p = 0.31).

CONCLUSIONS

Compliance with therapeutic dose of UFH during pregnancy in women with mechanical heart valves is associated with a low risk of valve thrombosis and good fetal outcomes, but meticulous monitoring is essential.

Monitoring of Anti-Xa in Pregnant Patients With Mechanical Prosthetic Valves Receiving Low-Molecular-Weight Heparin

Objectives:

We hypothesized that the guideline-recommended peak anti-Xa levels for pregnant women with mechanical prosthetic heart valves (MPHVs) receiving adjusted dose low-molecular-weight heparin (LMWH) are associated with subtherapeutic trough levels and consequently with an inadequate level of anticoagulation.

Background:

Low-molecular-weight heparin is often used for anticoagulation in pregnant women including those with MPHV. American College of Cardiology/American Heart Association guidelines recommend monitoring of plasma anti-Xa factor peak levels and adjustment of the dose to achieve peak levels of 0.7 to 1.2 U/mL. In spite of these recommendations, cases of valve thrombosis during pregnancy continue to occur.

Methods and Results:

We studied 30 pregnant patients receiving anticoagulation for various indications with adjusted dose LMWH given subcutaneously twice a day which had both trough and peak anti-Xa levels throughout pregnancy for a total of 187 paired determinations. The recommended peak anti-Xa levels (0.7-1.2 U/mL) were obtained in 123 (66%) of the measurements but in 80% of them, the trough levels were found to be subtherapeutic (<0.6 U/mL). Subtherapeutic trough levels were found in 8 (73%) of the 11 measurements with peak levels of 0.7 to 0.79 U/mL, 17 (74%) of the 23 of 0.8 to 0.89 U/mL, 21 (72%) of the 29 of 0.9 to 0.99 U/mL, and 28 (44%) of the 63 of 1.0 to 1.2 U/mL. There were 42 measurements with peak anti-Xa levels >1.2 U/mL and even in these cases, 13 (31%) of the trough levels were found to be subtherapeutic.

Conclusions:

Anticoagulation with adjusted dose LMWH aimed to achieve guideline-recommended peak levels of anti-Xa for patients with MPHVs is commonly associated with subtherapeutic trough levels. Routine measurement of trough anti-Xa levels is therefore advisable in women with MPHV treated with LMWH during pregnancy to assure adequate level of anticoagulation.

The effect of warfarin dosage on maternal and fetal outcomes in pregnant women with prosthetic heart valves

There are several challenges in the management of pregnant women with mechanical heart valves. Pregnancy increases the risk of thromboembolism and there is currently no consensus on the safest anticoagulation method during pregnancy. The objective of the study was to determine the correlation between the warfarin dose and pregnancy outcome in pregnant women with prosthetic heart valves. Warfarin in pregnancy was associated with a low risk of valve thrombosis or maternal death. The risk for fetal abnormalities was not related to the maternal warfarin dosage. However, the risk for stillbirth was significantly increased with increasing doses of warfarin.

Fluctuations in anti-factor Xa levels with therapeutic enoxaparin anticoagulation in pregnancy

OBJECTIVE

The objective of the study was to evaluate anti-factor Xa levels with therapeutic enoxaparin anticoagulation in pregnancy.

STUDY DESIGN

A total of 15 pregnant subjects on therapeutic doses of enoxaparin (1 mg/kg +/-20% subcutaneously (s.c.) twice daily (b.i.d.)) were enrolled prospectively in this cross-sectional pilot project. Three blood levels for anti-factor Xa activity were examined: before the enoxaparin dose (trough), 3- to 4-h later (peak) and 8-h later. Anti-factor Xa activity level between 0.5 and 1.2 U/ml was considered therapeutic.

RESULT

Mean anti-factor Xa activity levels were: trough 0.45+/-0.18, peak 0.9+/-0.25 and 8-h after dose 0.72+/-0.23 U/ml. All peak levels were therapeutic; 20% (3/15) of the 8 h and 73% (11/15) of the trough levels were sub-therapeutic.

CONCLUSION

Trough and 8-h post-dose anti-factor Xa activity levels were sub-therapeutic in a substantial number of patients receiving a b.i.d. regimen of therapeutic enoxaparin.

Use of high intensity adjusted dose low molecular weight heparin in women with mechanical heart valves during pregnancy: a single-center experience

The use of standard dose low molecular weight heparin (LMWH) to anticoagulate women with mechanical valves in pregnancy is associated with morbidity and mortality. We conducted a prospective audit of the use of adjusted dose high intensity LMWH in 12 pregnancies in 11 women with prosthetic heart valves. LMWH +/- low-dose aspirin was started at therapeutic-dose with monitoring of anti-Xa levels to achieve a target level of 1.0-1.2 IU/mL (0.8-1.2 in the first 3/12 pregnancies). This necessitated a mean increase in the dose of LMWH of 54.4% (SD+/-33.2) over initial dose. Eleven of 12 pregnancies resulted in live births, with one intrauterine fetal death at 37 weeks. One non-fatal valve thrombosis occurred at 26 weeks gestation associated with subtherapeutic anti-Xa levels. Three patients experienced major bleeding. This regime provides a therapeutic option for women with mechanical heart valves during pregnancy, provided anti-Xa levels are kept within the target range. These patients require close surveillance for bleeding and thrombotic complications within a multi-disciplinary setting.

Use of low molecular weight heparin in pregnant women with mechanical heart valves

There are a number of different anticoagulation options for pregnant women with mechanical heart valves. The purpose of this study was to examine maternal thromboembolic complications in women with mechanical valves treated with low-molecular weight heparin (LMWH) throughout pregnancy. This was a substudy of a larger prospective cohort study of pregnant women with heart disease followed from 1998 to 2008. All pregnant women with mechanical left-sided valves who were treated with LMWH throughout pregnancy were included. Maternal thromboembolic events were defined as valve thrombosis, need for valve replacement, or stroke during pregnancy or postpartum (up to 6 months). Twenty-three pregnancies (17 women) occurred in women treated with LMWH and low-dose aspirin: 15 in women with mechanical mitral valves, 9 in women with mechanical aortic valves, and 1 in a woman with both. There was 1 maternal thromboembolic event (4%), which resulted in maternal and fetal death. Five women (22%) developed other adverse cardiac events during pregnancy. Nine pregnancies (43%) had fetal or neonatal adverse events, 5 of which had favorable outcomes. Three pregnancies were complicated by postpartum hemorrhage. In conclusion, carefully monitored LMWH may be a suitable anticoagulation strategy in pregnant women with mechanical heart valves who are unwilling to use warfarin. However, this group of women remains at risk for maternal cardiac and fetal complications. The occurrence of valve thrombosis resulting in maternal death despite therapeutic anti-Xa levels highlights current limitations with anticoagulation in this population.

MECHANICAL HEART VALVES AND PREGNANCY

Mechanical heart valves pose a particular challenge in pregnancy, as the primary agent used to prevent valve thrombosis, coumadin (warfarin), is a known teratogen. Alternatives to coumadin, such as unfractionated heparin (UFH) and low-molecular weight heparin (LMWH) are safer for the fetus, particularly during the first trimester of pregnancy, but expose the mother to potential valve failure. This review will examine these controversies and the complex literature regarding management in pregnancy.

Prevention and management of venous thromboembolism in pregnancy

Normal pregnancy is accompanied by an increase in clotting factors. The resulting hypercoagulable state has likely evolved to protect women from hemorrhage at the time of miscarriage and childbirth. During pregnancy, women are 4 times more likely to suffer from venous thromboembolism (VTE) compared with when they are not pregnant. Relative to pregnancy, the risk postpartum is even higher. The incidence of VTE is approximately 2 per 1,000 births, and VTE accounts for 1 death per 100,000 births, or approximately 10% of all maternal deaths. The most important risk factors during pregnancy are thrombophilia and a history of thrombosis. A history of thrombosis increases the risk for VTE to 2% to 12%. Thrombophilia increases not only the risk for maternal thrombosis but also the risk of poor pregnancy outcome. Despite the increased risk for thrombosis during pregnancy and the postpartum period, most women do not require anticoagulation. Those who do require anticoagulation include women with current VTE, women on lifelong anticoagulation, and many women with thrombophilia or a history of thrombosis. Recommended options for anticoagulation in pregnancy are limited to heparins, which do not cross the placenta. Low-molecular-weight heparin (LMWH) is preferred over unfractionated heparin because LMWH has a longer half-life and is presumed to have fewer side effects. The longer half-life is a disadvantage around the time of delivery, when unfractionated heparin, with its shorter half-life, is easier to manage. For women who develop or are at high risk for heparin-induced thrombocytopenia or severe cutaneous reactions, fondaparinux is probably the agent of choice. Women who do not require lifelong anticoagulation, but require anticoagulation during pregnancy, will still require anticoagulation for the first 6 weeks postpartum.

Low molecular weight heparin treatment in pregnant women with a mechanical heart valve prosthesis

No definitive recommendation is available concerning optimal antithrombotic therapy in pregnant women with a mechanical heart valve. The purpose of the current study was to evaluate the clinical results of nadroparin treatment with respect to pregnancy outcome and maternal complications. From 1997 to 2005, 31 pregnancies were reviewed in 25 women. Nadroparin (7,500 U, twice daily) was used in 23 pregnancies between 6 and 12 weeks of gestation and close-to-term only, and coumarin derivatives were used with aspirin at other times. Eight pregnant women treated with coumarin derivatives throughout pregnancy were compared to evaluate the safety and efficacy of nadroparin. No maternal death or bleeding complication occurred in either of the two groups, and frequencies of maternal thromboembolism including valve thrombosis (8.7% vs. 12.5%, p>0.05) were similar. However, the frequencies of live born (91.3% vs. 50%, p=0.01) and healthy babies (90.4% vs. 25%, p<0.01) were significantly higher, and the fetal loss rate was significantly lower (8.7% vs. 50%, p=0.01) in the nadroparin-treated group. Regarding the efficacy and safety of antithrombotic treatment in pregnant women with prosthetic heart valves, nadroparin treatment during the first trimester is an acceptable regimen and produces better results than coumarin derivatives.

Venous Thromboembolism in Obstetrics and Gynecology

The diagnosis of venous thromboembolism can present a clinical challenge. Using D-dimer testing and spiral or helical computed tomography scans has simplified the diagnosis of venous thromboembolism. In addition, the use of low molecular weight heparin has become widely accepted in the prevention and treatment of venous thromboembolism. However, further studies are needed to determine optimal prevention and treatment strategies, particularly in the obstetric population.

Low-molecular-weight heparin for thromboprophylaxis in pregnant women with mechanical heart valves

BACKGROUND

Pregnancy in a woman with a mechanical heart valve is a life-threatening situation. Due to the inability of unfractionated heparin to prevent valvular thromboses, warfarin or other vitamin K antagonists have been the preferred anticoagulants for the mother. They are, however, potentially harmful to the fetus. With the advent of low-molecular-weight heparins, clinicians were hopeful for an alternative that was safe for the fetus, but more effective than unfractionated heparin, which carries a 29-33% risk of life-threatening thromboses and a 7-15% chance of mortality. Unfortunately, fatal thromboses have occurred with low-molecular-weight heparin as well.

METHODS

We searched the MEDLINE database and other sources to identify cases of the use of low-molecular-weight heparin for thromboprophylaxis in women with mechanical heart valves.

RESULTS

We found 73 cases and added three of our own for a total of 76. There were 17 thrombotic events (22%). Thirteen were valve thromboses, two were strokes, and two were myocardial infarctions. There were three deaths (4%).

CONCLUSIONS

While pregnant women with mechanical heart valves who receive low-molecular-weight heparin for thromboprophylaxis are at extremely high risk of life-threatening thromboses, there is no evidence that low-molecular-weight heparin is inferior to unfractionated heparin.

Anticoagulants in Pregnancy

Pregnancy is a hypercoagulable state that increases the risk of thromboembolic events. These risks may be further increased in the presence of an acquired or inherited thrombophilia. Thrombophilias have been associated with both maternal and fetal complications. The use of anticoagulants during pregnancy may reduce the risk of maternal thromboses as well as the risk of adverse pregnancy outcomes. The choice of an anticoagulant requires consideration of maternal risks, potential for teratogenicity, the underlying condition necessitating the treatment, and cost. This review examines the options for anticoagulation, the clinical situations that may warrant such treatment, and factors to be considered at delivery and during the postpartum period.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to describe the roles of acquired and inherited thrombophilia in furthering the hypercoagulable state of pregnancy, identify the potential consequences of using anticoagulants during pregnancy, and summarize the treatment options when anticoagulation is required during pregnancy.

Valvular Heart Disease and Pregnancy

A large number of prosthetic heart valves (PHV) are being implanted in patients with both congenital and acquired valvular disease. Many of the recipients of such valves are women of childbearing age who desire to have children. The main issues involved with pregnancy in a patient with PHV include the selection of PHV in women during their childbearing age, risks to both the mother and the fetus associated with pregnancy and the management of the patients with PHV during gestation.

Minimising the risk of heparin-induced osteoporosis during pregnancy

Unfractionated heparin (UFH) may lead to symptomatic vertebral fractures in up to 3 out of every 100 people on long-term therapy. Ten-times that many people will experience a significant reduction in bone density leading to osteopoenia or osteoporosis. Low molecular weight heparins (LMWH) have been shown to be as effective as UFH in the prevention and treatment of venous thromboembolism. Several well-established advantages of LMWH over UFH include increased bioavailability, more predictable dose response, less intensive coagulation monitoring, and a lower probability of causing immune-mediated thrombocytopenia. There is also some evidence that long-term LMWH therapy is less likely to cause osteoporotic fractures and significant reductions in bone mass than UFH. Both UFH and LMWH undergo pharmacokinetic changes during pregnancy, which sometimes necessitates dosage adjustments. Fondaparinux is a synthetic antithrombotic agent, which specifically binds to antithrombin. It has been shown to be comparable to, or even more effective than, LMWH in the management of both arterial and venous thrombosis. Fondaparinux does not appear to have a negative effect on bone metabolism. Therefore, fondaparinux may be a safe and effective alternative to UFH and LMWH in women who require anticoagulation during pregnancy.

Low-molecular-weight heparins for thromboprophylaxis and treatment of venous thromboembolism in pregnancy: a systematic review of safety and efficacy

To assess the safety and efficacy of low-molecular-weight heparins (LMWHs) for thromboprophylaxis and treatment of venous thromboembolism (VTE) in pregnancy, a systematic review of studies to the end of 2003 was undertaken. Data on VTE recurrence and side effects were extracted and cumulative incidences of VTE and adverse effects calculated. Of 81 reports identified, 64 reporting 2777 pregnancies were included. In 15 studies (174 patients) the indication for LMWH was treatment of acute VTE, and in 61 studies (2603 pregnancies) it was thromboprophylaxis or adverse pregnancy outcome. There were no maternal deaths. VTE and arterial thrombosis (associated with anti-phospholipid syndrome) were reported in 0.86% (95% confidence interval [CI], 0.55%-1.28%) and 0.50% (95% CI, 0.28%-0.84%) of pregnancies, respectively. Significant bleeding, generally associated with primary obstetric causes, occurred in 1.98% (95% CI, 1.50%-2.57%), allergic skin reactions in 1.80% (95% CI, 1.34%-2.37%), heparin-induced thrombocytopenia in 0%, thrombocytopenia (unrelated to LMWH) in 0.11% (95% CI, 0.02%-0.32%), and osteoporotic fracture in 0.04% (95% CI, < 0.01%-0.20%) of pregnancies. Overall, live births were reported in 94.7% of pregnancies, including 85.4% in those receiving LMWH for recurrent pregnancy loss. LMWH is both safe and effective to prevent or treat VTE in pregnancy.

Pregnancy outcome in women with prosthetic heart valves

OBJECTIVE

This study was undertaken to evaluate the risks and pregnancy outcome in women with prosthetic heart valves on different anticoagulent regimens.

STUDY DESIGN

A retrospective chart review of 82 pregnancies in 33 women with mechanical valve prostheses at a tertiary referral center from 1987 to 2002. The main outcome measures were major maternal complications and perinatal outcome.

RESULTS

The valve replaced was mitral (60.6%), aortic (18.2%), and both (21.2%). Fifty-four pregnancies (65.9%) resulted in live births, 9 (11.0%) had stillbirths (all on warfarin), and 12 (14.6%) had spontaneous and 7 (8.5%) therapeutic abortions (all on warfarin). The rate of spontaneous abortion was highest in women on warfarin throughout pregnancy (P < .01). The live birth rate was higher in women on heparin compared with those on warfarin (P < .01), and in those on heparin/warfarin compared with warfarin alone (P < .01). There were no maternal deaths; however, 3 patients had mitral valve thrombosis (2 on heparin and 1 on warfarin) necessitating surgery in 1 patient and medical thrombolysis in 2 patients. Hemorrhagic complications occurred in 5 patients, 4 of whom required transfusion.

CONCLUSION

No single anticoagulant regimen confers complete protection from thromboembolic phenomena in pregnancy. Despite a high maternal morbidity rate, the perinatal outcome is acceptable when pregnancy progresses beyond the first trimester.

Use of Antithrombotic Agents During Pregnancy

This chapter about the use of antithrombotic agents during pregnancy is part of the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following: for women requiring long-term vitamin K antagonist therapy who are attempting pregnancy, we suggest performing frequent pregnancy tests and substituting unfractionated heparin (UFH) or low molecular weight heparin (LMWH) for warfarin when pregnancy is achieved (Grade 2C). In women with acute venous thromboembolism (VTE), we recommend adjusted-dose LMWH throughout pregnancy or IV UFH for at least 5 days, followed by adjusted-dose UFH or LMWH for the remainder of the pregnancy and at least 6 weeks postpartum (Grade 1C+). In patients with a single episode of VTE associated with a transient risk factor that is no longer present, we recommend antepartum clinical surveillance and postpartum anticoagulants (Grade 1C). In patients with a single episode of VTE and thrombophilia or strong family history of thrombosis and not receiving long-term anticoagulants, we suggest antepartum prophylactic or intermediate-dose LMWH or minidose or moderate-dose UFH, plus postpartum anticoagulants (Grade 2C). In patients with multiple (two or more) episodes of VTE and/or women receiving long-term anticoagulants, we suggest antepartum adjusted-dose UFH or adjusted-dose LMWH followed by long-term anticoagulants postpartum (Grade 2C). For pregnant patients with antiphospholipid antibodies (APLAs) and a history of two or more early pregnancy losses or one or more late pregnancy losses, preeclampsia, intrauterine growth retardation, or abruption, we suggest antepartum aspirin plus minidose or moderate-dose UFH or prophylactic LMWH (Grade 2B). We suggest one of the following approaches for women with APLAs without prior VTE or pregnancy loss: surveillance, minidose heparin, prophylactic LMWH, and/or low-dose aspirin, 75 to 325 mg/d (all Grade 2C). In women with prosthetic heart valves, we recommend adjusted-dose bid LMWH throughout pregnancy (Grade 1C), aggressive adjusted-dose UFH throughout pregnancy (Grade 1C), or UFH or LMWH until the thirteenth week and then change to warfarin until the middle of the third trimester before restarting UFH or LMWH (Grade 1C). In high-risk women with prosthetic heart valves, we suggest the addition of low-dose aspirin, 75 to 162 mg/d (Grade 2C).

Cardiac disease in pregnancy

This article reviews the complications, management and prognosis of cardiac disease in pregnancy.

Prophylactic and therapeutic enoxaparin during pregnancy: Indications, outcomes and monitoring

OBJECTIVES

To evaluate the efficacy and safety of prophylactic and therapeutic enoxaparin in pregnancy.

STUDY DESIGN

Three-year prospective audit.

SETTING

Tertiary level obstetric hospital.

POPULATION

Fifty-two women who received subcutaneous enoxaparin, either a prophylactic dose (40 mg daily) in 26 pregnancies or therapeutic dose (1 mg/kg twice daily) in 32 pregnancies.

MATERIALS AND METHODS

Pregnant women treated with enoxaparin were prospectively entered into a register. Data were retrieved by case note review.

MAIN OUTCOME MEASURES

Pregnancy outcomes, treatment complications and anti-Xa levels.

RESULTS

In the prophylactic group there were no fetal losses, thromboembolic events or complications related to enoxaparin. In the therapeutic group there were four first trimester miscarriages, a termination and 27 live births. Therapeutic enoxaparin prevented further thromboembolism without complications. One woman was treated with intermediate dose enoxaparin when she presented at 5 weeks' gestation on warfarin and 7 weeks after a venous thromboembolism. She developed a recurrent pulmonary embolus 3 weeks later and was subsequently treated with therapeutic enoxaparin. In the therapeutic group the enoxaparin dose/kg correlated poorly with anti-Xa levels, and dose adjustments were made. Therapeutic mean (SD) trough and peak anti-Xa levels were 0.33 U/mL (0.14) and 0.86 U/mL (0.24) in the first trimester and 0.48 U/mL (0.19) and 0.84 U/mL (0.23) in the third trimester.

CONCLUSIONS

In the present series, prophylactic and therapeutic enoxaparin treatment during pregnancy was effective and safe. Studies are required to determine the optimal duration of treatment with therapeutic enoxaparin following venous thromboembolism in pregnancy and the clinical relevance of anti-Xa monitoring.

Use of the low-molecular-weight heparin nadroparin during pregnancy. A review

Antithrombotic therapy is often used during pregnancy for the treatment and prevention of venous thromboembolism, the prevention of systemic embolism in patients with heart valve prostheses and the prevention of foetal loss in patients with antiphospholipid syndrome. Low-molecular-weight heparins (LMWHs), including nadroparin, have largely replaced unfractionated heparin as the anticoagulant of choice. The use of the LMWH nadroparin in pregnant women at an increased risk of thromboembolism or foetal loss is discussed in this review. Deep vein thrombosis can be effectively treated or prevented with nadroparin without any serious adverse events. Nadroparin 0.1 ml/10 kg s.c. once daily prevents thromboembolic complications in pregnant women with heart valve prostheses. Nadroparin is also effective in preventing foetal loss, through contributing to normal placental development and in decreasing the risk of premature delivery in pregnant women with antiphospholipid syndrome or women with herpes and antiphospholipid syndrome. These results demonstrate nadroparin is effective, easy to administer and associated with a low incidence of foetal and maternal complications. The use of nadroparin at a prophylactic dose of 0.3 ml (2850 IU AXa, 95 IU/kg) (for high-risk patients, 0.3-0.6 ml) s.c. once daily, and a therapeutic dose of 0.1 ml/10 kg (95 IU/kg) s.c. twice daily, is in line with the latest international guidelines of the American College of Chest Physicans.

Review of enoxaparin and its clinical applications in venous and arterial thromboembolism

Venous and arterial thromboembolic disorders are common medical conditions that are associated with considerable morbidity and mortality. Unfractionated heparin (UFH) and its derivatives, the low molecular weight heparins (LMWHs), are the anticoagulants of choice when a rapid anticoagulant effect is required. LMWHs have several advantages over UFH, including a longer plasma half-life and higher bioavailability; a predictable dose response, which enables once- or twice-daily dosing; and a more convenient route of administration (subcutaneous instead of intravenous), which enables patients to self-inject in an out-patient setting. Enoxaparin is a LMWH prepared by alkaline hydrolysis of the benzylin ester of UFH. The efficacy of enoxaparin in the management of venous and arterial thromboembolism has been shown in a wide range of patient groups using doses ranging from fixed doses of 20 - 60 mg o.d. and 0.75 - 1.5 mg/kg b.i.d. Other doses, such as 80 mg/day for pregnant women with combined thrombophilic defects, have also been studied. The use of subcutaneous enoxaparin as an effective and safe home treatment for patients with acute proximal deep vein thrombosis (DVT) has been demonstrated. The benefits of preventing venous thromboembolic events with enoxaparin include reducing the costs associated with investigating the symptoms of DVT, acute treatment and hospitalisation, and potentially the development of post-thrombotic syndrome, while improving quality of life and so making the treatment cost effective. In contrast to other LMWHs, enoxaparin has been shown to provide better outcomes than UFH in the treatment of unstable angina and non-ST-segment elevation myocardial infarction, without increasing major bleeding. Adverse events with enoxaparin are infrequent; the most common events are minor bleeding complications. It should be noted that different doses or indications are approved in each country.

Cardiac disease in pregnancy

Congenital heart disease in pregnancy is increasingly common because of the advances in surgery and medical therapy which have taken place over the last 30 years, which means that more affected women are surviving into the reproductive age. Antenatal counselling needs to be tailored to the specific lesion, with pulmonary hypertension and cyanotic disease presenting a risk of maternal mortality of up to 50%. The use of anticoagulants in women with artificial valves presents a particular challenge, heparin being safer for the baby and warfarin for the mother. Peripartum cardiomyopathy and Marfan's syndrome may be less dangerous than once thought. The risk of congenital heart disease in the fetus is increased, from twice to 20-fold, depending on the nature of the mother's lesion. Care throughout pregnancy and in the puerperium should be multidisciplinary and include cardiologists, obstetricians and midwives with experience of such cases, preferably in a tertiary centre.