Postpartum Bone Mineral Density in Women Treated for Thromboprophylaxis with Unfractionated Heparin or LMW Heparin

Management of women with recurrent pregnancy losses and antiphospholipid antibody syndrome

Antiphospholipid antibodies (aPL) have been associated with recurrent pregnancy losses (RPL) and other obstetrical complications. The diagnostic criteria for the classical antiphospholipid antibody syndrome (APS) have been utilized for the detection of obstetrical APS in women with RPL. However, laboratory findings and immunopathology of obstetrical APS are significantly different from those of classical APS. In addition, many women with RPL who have positive aPL do not have symptoms consistent with the current APS criteria. The induction of a proinflammatory immune response from trophoblasts and complement activation by aPL rather than thromboembolic changes has been reported as a major immunopathological feature of obstetrical APS. Heparin treatment has been reported to be effective in prevention of early pregnancy loss with APS but not for the late pregnancy loss or complications. The complex effects of heparin may explain the limited efficacy of heparin treatment in RPL. New diagnostic criteria for obstetrical APS are needed urgently, and new therapeutic approaches should be explored further.

[Long-term low-molecular-weight heparin therapy during pregnancy: is there a bone risk?]

Unfractionated heparin (UFH) and low-molecular-weight heparins (LMWH) are broadly used for the thromboprophylaxis during pregnancy. Long-term heparin therapy has raised concern about the risk of bone loss and osteoporotic fractures while pregnancy by itself favors osteoporosis. Experimental studies show a comparable effect of UFH and LMWH on bone formation while UFH has a more marked effect on bone resorption. Available clinical studies do not provide evidence of a difference between UFH and LMWH or among different LMWH on the bone risk. However, clinical studies show that bone loss observed with LMWH is not different from the physiological loss related to pregnancy, and osteoporotic fractures are associated with comorbidities or osteoporosis risk factors. LMWH represent the preferred alternative for thromboprophylaxis during pregnancy.

Venous thromboembolism associated with pregnancy and hormonal therapy

Venous thromboembolism (VTE) is a major cause of maternal morbidity and mortality during or early after pregnancy and in women taking hormonal therapy for contraception or for replacement therapy. Post-thrombotic syndrome, including leg oedema and leg pain, is an unrecognized burden after pregnancy-related VTE, which will affect more than two of five women. Women with a prior VTE, a family history of VTE, certain clinical risk factors and thrombophilia are at considerably increased risk both for pregnancy-related VTE and for VTE on hormonal therapy. This review critically assesses the epidemiology and risk factors for pregnancy-related VTE and current guidelines for prophylaxis and treatment. We also provide information on the risk of VTE related to hormonal contraception and replacement therapy.

Pregnancy-associated venous thromboembolism: prevention and treatment

Pregnancy is associated with an increased risk of venous thromboembolism (VTE) and this condition remains an important cause of maternal morbidity and mortality. The use of anticoagulant therapy for treatment and prophylaxis of VTE during pregnancy is challenging because of the potential for fetal, as well as maternal, complications. Although evidence-based recommendations for the use of anticoagulants have been published, given the paucity of available data, guidelines are based largely upon observational studies and from data in nonpregnant patients. This article reviews the available literature and provides guidance for the management and prevention of VTE during pregnancy.

Parenteral anticoagulants: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

This article describes the pharmacology of approved parenteral anticoagulants. These include the indirect anticoagulants, unfractionated heparin (UFH), low-molecular-weight heparins (LMWHs), fondaparinux, and danaparoid, as well as the direct thrombin inhibitors hirudin, bivalirudin, and argatroban. UFH is a heterogeneous mixture of glycosaminoglycans that bind to antithrombin via a unique pentasaccharide sequence and catalyze the inactivation of thrombin, factor Xa, and other clotting enzymes. Heparin also binds to cells and plasma proteins other than antithrombin causing unpredictable pharmacokinetic and pharmacodynamic properties and triggering nonhemorrhagic side effects, such as heparin-induced thrombocytopenia (HIT) and osteoporosis. LMWHs have greater inhibitory activity against factor Xa than thrombin and exhibit less binding to cells and plasma proteins than heparin. Consequently, LMWH preparations have more predictable pharmacokinetic and pharmacodynamic properties, have a longer half-life than heparin, and are associated with a lower risk of nonhemorrhagic side effects. LMWHs can be administered once daily or bid by subcutaneous injection, without coagulation monitoring. Based on their greater convenience, LMWHs have replaced UFH for many clinical indications. Fondaparinux, a synthetic pentasaccharide, catalyzes the inhibition of factor Xa, but not thrombin, in an antithrombin-dependent fashion. Fondaparinux binds only to antithrombin. Therefore, fondaparinux-associated HIT or osteoporosis is unlikely to occur. Fondaparinux exhibits complete bioavailability when administered subcutaneously, has a longer half-life than LMWHs, and is given once daily by subcutaneous injection in fixed doses, without coagulation monitoring. Three additional parenteral direct thrombin inhibitors and danaparoid are approved as alternatives to heparin in patients with HIT.

VTE, thrombophilia, antithrombotic therapy, and pregnancy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

The use of anticoagulant therapy during pregnancy is challenging because of the potential for both fetal and maternal complications. This guideline focuses on the management of VTE and thrombophilia as well as the use of antithrombotic agents during pregnancy.

METHODS

The methods of this guideline follow the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in this supplement.

RESULTS

We recommend low-molecular-weight heparin for the prevention and treatment of VTE in pregnant women instead of unfractionated heparin (Grade 1B). For pregnant women with acute VTE, we suggest that anticoagulants be continued for at least 6 weeks postpartum (for a minimum duration of therapy of 3 months) compared with shorter durations of treatment (Grade 2C). For women who fulfill the laboratory criteria for antiphospholipid antibody (APLA) syndrome and meet the clinical APLA criteria based on a history of three or more pregnancy losses, we recommend antepartum administration of prophylactic or intermediate-dose unfractionated heparin or prophylactic low-molecular-weight heparin combined with low-dose aspirin (75-100 mg/d) over no treatment (Grade 1B). For women with inherited thrombophilia and a history of pregnancy complications, we suggest not to use antithrombotic prophylaxis (Grade 2C). For women with two or more miscarriages but without APLA or thrombophilia, we recommend against antithrombotic prophylaxis (Grade 1B).

CONCLUSIONS

Most recommendations in this guideline are based on observational studies and extrapolation from other populations. There is an urgent need for appropriately designed studies in this population.

Adverse effects of heparin

All the adverse effects of heparins are related to their wide variety of biological activities, with bleeding being the most important safety issue, resulting directly from the potency of heparin as an anticoagulant. However, it is hard to define the bleeding risk, since it depends on numerous parameters including the indication, dosage, method, and duration of heparin application, the clinical study design and definition of bleeding as well as patient characteristics and determinants of bleeding such as type of surgery and co-medication. Nonbleeding complications of heparins are caused by binding of heparin molecules to proteins other than antithrombin and to cells, which is generally more pronounced with unfractionated heparin than with low-molecular-weight heparins. Accordingly, heparin-induced thrombocytopenia, the most severe nonbleeding adverse reaction, occurs about 10 times less with low-molecular-weight heparins than with unfractionated heparin. Frequent and therefore important adverse reactions of heparins are skin lesions resulting from delayed-type hypersensitivity reactions. All the other undesirable effects are discussed as well, but they are mostly clinically irrelevant.

Thromboembolism in the obese pregnant woman

We sought to quantify the added risk of thromboembolism in the obese parturient, evaluate risk factors for thromboembolism in the obese parturient, and provide suggestions as to when and in what form thromboembolism prophylaxis should be considered. Although recent guidelines from national colleges and advisory groups have attempted to guide the clinician in thromboprophylaxis in the obese parturient, the lack of adequate prospective series and trials has lead to some contrary recommendations. The arbitrary use of bed rest in the obese patient is a significant risk factor for venous thromboembolism without proven benefit. Despite a paucity of gold standard evidence, the prevalence of obesity and its associated risk of venous thromboembolism warrants careful consideration for the use of thromboprophylaxis in the obese pregnant population. This is especially important in the presence of additional thromboembolism risk factors.

How I treat pregnancy-related venous thromboembolism

Venous thromboembolism (VTE) complicates ∼ 1 to 2 of 1000 pregnancies, with pulmonary embolism being a leading cause of maternal mortality and deep vein thrombosis an important cause of maternal morbidity, also on the long term. However, a strong evidence base for the management of pregnancy-related VTE is missing. Management is not standardized between physicians, centers, and countries. The management of pregnancy-related VTE is based on extrapolation from the nonpregnant population, and clinical trial data for the optimal treatment are not available. Low-molecular-weight heparin (LMWH) in therapeutic doses is the treatment of choice during pregnancy, and anticoagulation (LMWH or vitamin K antagonists postpartum) should be continued until 6 weeks after delivery with a minimum total duration of 3 months. Use of LMWH or vitamin K antagonists does not preclude breastfeeding. Whether dosing should be based on weight or anti-Xa levels is unknown, and practices differ between centers. Management of delivery, including the type of anesthesia if deemed necessary, requires a multidisciplinary approach, and several options are possible, depending on local preferences and patient-specific conditions.

Tinzaparin use in pregnancy: an international, retrospective study of the safety and efficacy profile

OBJECTIVES

This study audited pregnancies where the mother received tinzaparin (at any stage before delivery), with a primary objective of determining the maternal safety of this low molecular weight heparin when administered as treatment and/or prophylaxis; the secondary objective was to audit fetal and neonatal safety in this cohort. Efficacy outcomes were also recorded.

STUDY DESIGN

The audit period was 1996-2009; consecutive, retrospective pregnancy records at participating hospitals were reviewed. For those records documenting tinzaparin use and pregnancy outcome, information was extracted into a standardised case report form; these were reviewed for adverse events, which were submitted for adjudication by independent experts in obstetric medicine and haematology. Endpoints were presented using descriptive statistics for all pregnancies, and by reason for tinzaparin use (treatment of venous thromboembolism [VTE] and prophylaxis).

RESULTS

There were 28 participating hospital centres in eight countries (Belgium, Canada, Denmark, Ireland, Netherlands, Sweden, Spain and the UK). Data were collected from 1267 pregnancies (1120 women; 1303 fetuses); in 254 pregnancies the women received tinzaparin as treatment (median dose 13,000 international units [IU]/day, range 3500-23,100IU/day; median duration 72 days; 94.1% once-daily), and in 1013 pregnancies the women received tinzaparin for prophylaxis (median dose 4500IU/day, range 2500-21,811IU/day, median duration 183 days, 94.6% once-daily). There were 871 (70.2%) vaginal deliveries (78 assisted) and 369 (29.8%) caesarean sections (27 delivery data missing). Overall, 495 (39.3%) women had neuraxial anaesthesia; however, there were no reported associated haematomas. There were no maternal deaths. Of pregnancies with available data (1060), 86.9% had blood loss ≤500mL, 11.0% of >500 to ≤1000mL, 0.9% >1000 to ≤1500mL and 1.1% >1500mL. There were 1245 (95.5%) live births, 15 (1.2%) stillbirths, 40 (3.1%) miscarriages and 3 (0.2%) terminations. Six (0.5%) neonatal deaths occurred (five at <27 weeks, one Ebstein's anomaly). No neonatal haemorrhages occurred. Adjudicated safety outcomes included 125 (9.9%) 'any bleeding' cases considered related to tinzaparin; 16 (1.3%) of these required medical intervention. In the treatment group, five (2%) recurrent VTEs were reported and 10 (1%) occurred in the prophylaxis group.

CONCLUSIONS

These data provide reassuring maternal and fetal outcome information in pregnancies exposed to tinzaparin.

Pregnancy and pulmonary hypertension

When pulmonary hypertension (PH) occurs in pregnancy, physiologic stress can overwhelm an already strained right ventricle resulting in right ventricular failure and death. Mortality remains unacceptably high (25%-30%). Patients with PH should be counseled to avoid pregnancy. This article discusses the physiologic changes of pregnancy that make it difficult for patients with PH, the pitfalls of transthoracic echocardiography in diagnosing PH in pregnancy, and the historical data regarding mortality. The causes of development of PH during pregnancy are discussed, and the limited data on management of patients with PH who choose to carry their pregnancy to term are reviewed.

Peripartum pulmonary embolism

Pregnancy is an example of Virchow's triad predisposing to the development of venous thromboembolism (VTE). Specific risk factors for antepartum and postpartum VTE have been identified. The diagnosis of pulmonary embolism in pregnancy is complicated by the physiologic changes of pregnancy as well as physicians' apprehension about ordering radiologic studies during pregnancy because of concerns with fetal well-being. Therapy for VTE is complicated by pregnancy physiology affecting medication pharmacokinetics and bioavailability, and the unpredictable occurrence of labor during therapeutic anticoagulation.

New frontiers with bemiparin: use in special populations

Special populations are rarely included in conventional clinical trials and subsequently there is a lack of guidance on the appropriate treatment regimens to use. This paper reviews data on the use of bemiparin in such populations, including the elderly, those with renal impairment, pregnant women and children. Pharmacokinetic data from elderly patients suggest that bemiparin is also safe in this patient population. There was no evidence of the accumulation of bemiparin after repeated prophylactic doses. At therapeutic doses, there was no significant difference in pharmacokinetic profile between groups. There is no need for dose adjustment of bemiparin in the elderly, either during prophylaxis or during treatment. Data from another pharmacokinetic study showed that bemiparin at prophylactic doses is safe in patients with mild to moderate renal impairment. In general, no dose adjustment was required in patients with mild to moderate renal impairment when bemiparin is used as therapy or prophylaxis. To date, bemiparin has not been tested in patients with severe renal impairment; therefore, conclusions on the safety of bemiparin in patients with severe renal failure cannot be drawn at present. Although there are no published data on the use of bemiparin in pregnant women, promising anecdotal data are beginning to emerge. Current guidelines recommend low molecular weight heparins (LMWH) for the treatment of venous thromboembolism (VTE) in pregnant women, with treatment maintained at therapeutic doses throughout pregnancy. Anticoagulation should continue for 6 weeks or more post-partum and should be maintained for 3 months or more after diagnosis of the VTE event. Monitoring of pregnant women receiving LMWH is not necessary, except in those at high risk. A case report describing the treatment of a neonate with renal vein thrombosis showed that 2 months' treatment with bemiparin followed by 10 months' prophylaxis was effective and safe. These data suggest that bemiparin may play a role in the treatment of VTE in paediatric patients.

[Initial antithrombotic therapy for pulmonary embolism]

The initial therapy for patients with pulmonary embolism who are haemodynamically stable relies on antithrombotic treatment. The aim of anticoagulant treatment is to prevent any thrombus extension or recurrence, with revascularization dependent on the fibrinolytic system. Current treatment is biphasic, with parenteral heparin or derivatives (low molecular weight heparins and fondaparinux) followed by oral vitamin K antagonists. Although these treatments are efficient, they suffer from some limitations including parenteral administration and the need for surveillance and monitoring. Use of low molecular weight heparins or fondaparinux is recommended in French guidelines, but unfractionated heparin still has an important role in some specific situations such as severe renal insufficiency, around the time of surgery and where there is a high risk of bleeding. The next generation of anticoagulants will soon be licensed for treatment in pulmonary embolism and may well replace heparin and/or vitamin K antagonists for the majority of patients, although "older" treatments will always be requested in some specific situations.

Venous thromboembolism in pregnancy

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

Influence of long-term thromboprophylaxis with low-molecular-weight heparin (enoxaparin) on changes of bone metabolism markers in pregnant women

This is a first descriptive, retrospective, observational study aiming to evaluate the changes in bone turnover markers in pregnant women and to assess the effect of a long-term treatment with low-molecular-weight heparin (LMWH), specifically, enoxaparin. Study involved 50 pregnant Caucasian women with thrombophilia. The patients either received prophylactic enoxaparin once daily subcutaneously (N = 35) or were observed without treatment (N = 15). Concentrations of total serum alkaline phosphatase (total AP), bone alkaline phosphatase (bone AP), osteoprotegerin (OPG), and the receptor activator of nuclear factor κB ligand (RANKL) were measured at 15, 25, and 35 weeks of gestation. Total serum AP increased with gestational age. In the group treated with enoxaparin, the percentage of bone AP concentration was lower (P < .05) than in the control group. Serum OPG also increased with gestational age, but no significant difference was found between the groups with- and without treatment. Despite the OPG increased, RANKL did not change.

Drug-induced osteoporosis in the older adult

The elderly population is at risk for polypharmacy and, therefore, also at risk for drug-induced osteoporosis (DIOP). Epidemiologic studies provide valuable information about medications that may place patients at risk for DIOP. While glucocorticoids are the most common cause of DIOP, the use of several other therapeutic agents can place patients at risk for significant bone loss and fracture. These medications include, but are not limited to, aromatase inhibitors, gonadotropin-releasing hormone agonists, thyroid replacement therapy, antiepileptics, antidepressants, antipsychotics, lithium, gastric acid lowering agents, thiazolidinediones, loop diuretics, heparins and warfarin, vitamin A and cyclosporine. This article provides information about their mechanism of action, studies that have evaluated these agents in DIOP and prevention and treatment strategies.

Anticoagulant therapy for deep vein thrombosis (DVT) in pregnancy

BACKGROUND

Thromboembolic complications are much higher in pregnancy due to procoagulant changes. Heparin does not cross the placenta and the use of unfractionated heparin (UFH) is the current established practice in prophylaxis and treatment for thromboembolism in pregnancy.

OBJECTIVES

To compare the effectiveness of anticoagulant therapies for the treatment of deep vein thrombosis in pregnancy. The anticoagulant drugs included are UFH, low molecular weight heparin (LMWH) and warfarin.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (March 2010) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials comparing any combination of warfarin, UFH, LMWH and placebo in pregnant women.

DATA COLLECTION AND ANALYSIS

We used methods described in the Cochrane Handbooks for Systemic Reviews of Interventions for assessing the eligibility of studies identified by the search strategy. A minimum of two review authors independently assessed each study.

MAIN RESULTS

We did not identify any eligible studies for inclusion in the review.We identified three potential studies; after assessing eligibility, we excluded all three as they did not meet the prespecified inclusion criteria. One study compared LMWH and UFH in pregnant women with previous thromboembolic events and, for most of these women, anticoagulants were used as thromboprophylaxis. There were only three women who had a thromboembolic event during the current pregnancy and it was unclear whether the anticoagulant was used as therapy or prophylaxis. We excluded one study because it included only women undergoing caesarean birth. The third study was not a randomised trial.

AUTHORS' CONCLUSIONS

There is no evidence from randomised controlled trials on the effectiveness of anticoagulation for deep vein thrombosis in pregnancy. Further studies are required.

Prophylaxis for venous thromboembolic disease in pregnancy and the early postnatal period

BACKGROUND

Venous thromboembolic disease (TED), although rare, is a major cause of maternal mortality and morbidity, hence methods of prophylaxis are often used for women at risk. This may include women delivered by caesarean section, those with a personal or family history of TED and women with inherited or acquired thrombophilias (conditions that predispose people to thrombosis). Many methods of prophylaxis carry a risk of side effects, and as the risk of TED is low, it is possible that the benefits of thromboprophylaxis may be outweighed by harm. Current guidelines for clinical practice are based on expert opinion only, rather than high quality evidence from randomised trials.

OBJECTIVES

To determine the effects of thromboprophylaxis in women who are pregnant or have recently delivered and are at increased risk of TED on the incidence of venous TED and side effects of treatment.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (May 2009).

SELECTION CRITERIA

Randomised trials comparing one method of thromboprophylaxis with placebo or no treatment, and randomised trials comparing two (or more) methods of thromboprophylaxis.

DATA COLLECTION AND ANALYSIS

Two review authors extracted data independently and resolved any discrepancies by discussion.

MAIN RESULTS

Sixteen trials met the inclusion criteria but only 13 trials, involving 1774 women, examining a range of methods of thromboprophylaxis, contributed data for the outcomes of interest. Four of them compared methods of antenatal prophylaxis: low molecular weight heparin (LMWH) versus unfractionated heparin (UFH) (two studies), and heparin versus no treatment (two studies). Eight studies assessed postnatal prophylaxis after caesarean section; one compared hydroxyethyl starch with unfractionated heparin; four compared heparin with placebo; and the other three compared UFH with LMWH. One study examined prophylaxis in the postnatal period.The small number of statistically significant findings in this review are largely derived from trials which are not of high methodological quality. It was not possible to assess the effects of any of these interventions on most outcomes, and especially on rare outcomes such as death, TED and osteoporosis, because of small sample sizes and the small number of trials making the same comparisons.There was some evidence of side effects associated with thromboprophylaxis.

AUTHORS' CONCLUSIONS

There is insufficient evidence on which to base recommendations for thromboprophylaxis during pregnancy and the early postnatal period. Large scale randomised trials of currently-used interventions should be conducted.

Safety evaluation of enoxaparin in currently approved indications

BACKGROUND

Potential limitations of unfractionated heparin (UFH) have prompted a search for new antithrombin therapies in recent years. Enoxaparin has shown similar or improved efficacy when compared with UFH, but it has been associated with safety concerns of increased bleeding in patients with acute coronary syndromes in some studies.

OBJECTIVE

This narrative review focuses on the safety and tolerability of enoxaparin in adult patients in the setting of currently approved indications.

METHODS

Synthesis of evidence from recent trials, systematic reviews, meta-analyses, regulatory documents and clinical trials registries of manufacturers.

CONCLUSION

Enoxaparin can be considered for prophylaxis and treatment of a wide range of thrombotic conditions as an alternative to UFH with a clinically modest increase in bleeding complications, without altering the risk-benefit profile of this compound. Selection of the appropriate dosage is strongly recommended. Special precautions should be taken in specific populations that are at higher risk of bleeding, such as patients with renal dysfunction and elderly patients, where dose adjustment is recommended.

Pulmonary embolism in pregnancy

Pulmonary embolism (PE) is the leading cause of maternal mortality in the developed world. Mortality from PE in pregnancy might be related to challenges in targeting the right population for prevention, ensuring that diagnosis is suspected and adequately investigated, and initiating timely and best possible treatment of this disease. Pregnancy is an example of Virchow's triad: hypercoagulability, venous stasis, and vascular damage; together these factors lead to an increased incidence of venous thromboembolism. This disorder is often suspected in pregnant women because some of the physiological changes of pregnancy mimic its signs and symptoms. Despite concerns for fetal teratogenicity and oncogenicity associated with diagnostic testing, and potential adverse effects of pharmacological treatment, an accurate diagnosis of PE and a timely therapeutic intervention are crucial. Appropriate prophylaxis should be weighed against the risk of complications and offered according to risk stratification.

Evidence base for the management of venous thromboembolism in pregnancy

Venous thromboembolism (VTE), comprising deep vein thrombosis (DVT) and pulmonary embolism (PE), is a leading cause of maternal mortality during pregnancy. DVT and PE are commonly suspected due to many mimicking signs and symptoms that are normal in pregnancy. However, validated diagnostic approaches are lacking, and a fear of teratogenic/oncogenic exposure from imaging procedures affects the acceptability of diagnostic approaches used for VTE during pregnancy. DVT and PE treatment in pregnancy is also challenging due to this lack of validated diagnostic approaches, changes in maternal physiology, and the need for intact hemostasis at the time of delivery/epidural analgesia. Prevention requires an optimal balancing of absolute increased bleeding risk from pharmacologic thromboprophylaxis and the absolute benefit of reduced DVT and PE, which, while serious, are relatively uncommon.

A longitudinal study of the effect of heparin thromboprophylaxis during pregnancy on maternal bone metabolism

The aim of this study was to determine the effect of heparin thromboprophylaxis during pregnancy on maternal biochemical markers of bone metabolism. This was a prospective longitudinal study of carboxy terminal pro-peptide of type I collagen (PICP) and cross-linked carboxyterminal telopeptide of type I collagen (ICTP) levels in 15 women, who had heparin thromboprophylaxis during pregnancy compared with those of 18 normal pregnant controls. During pregnancy, the rate of change of PICP and ICTP in women who had heparin thromboprophylaxis was similar to those of women who did not (P = 0.184 for PICP, and P = 0.129 for ICTP), and PICP and ICTP levels at individual time points were similar in both groups. Therefore, heparin thromboprophylaxis during pregnancy does not affect maternal biochemical markers of bone metabolism.

Review: Low-molecular-weight heparin-induced osteoporosis and osteoporotic fractures: a myth or an existing entity?

Long-term use of unfractioned heparin data has been associated with a 2.2-5% incidence of heparin-induced osteoporotic fracture, but for low-molecular-weight heparin (LMWH) data is scarce and there is lack of clarity of the risks of osteoporosis and osteoporotic fractures. In this paper we review the differential diagnosis of osteoporosis and osteoporotic fractures, and we conduct a systematic review of all related cases from case reports and trials. Two new cases of possible LMWH-induced osteoporosis are also presented and the difficulties in making the diagnosis are highlighted. The authors conclude that, until large clinical trials are designed to investigate pre- and post-treatment bone density and to compare different dosages of LMWH effect on the bone density in different patient groups, no safe conclusions can be made.

How I treat the antiphospholipid syndrome

This article discusses how we approach medical decision making in the treatment of the various facets of the antiphospholipid syndrome (APS), including secondary prophylaxis in the setting of venous and arterial thrombosis, as well as treatment for the prevention of recurrent miscarriages and fetal death. The role of primary thromboprophylaxis is also discussed in depth. Great emphasis is given to incorporating the most up-to-date and relevant evidence base both from the APS literature, and from large, recent, randomized controlled trials (RCTs) of primary and secondary thrombotic prophylaxis in the general population setting (ie, the population that has not been specifically investigated for APS).

Obstetric disorders in the ICU

Obstetric disorders account for 55% to 80% of admissions to the intensive care unit in the obstetric population. Medical conditions are emerging as the leading cause of maternal mortality, partly because of marked improvement in surgical and obstetric care in the developed world. The rise in maternal mortality related to medical conditions can be explained by multiple factors: improved medical care, women with chronic illnesses reaching childbearing years, older age at time of first pregnancy, improved reproductive technologies, and severe medical conditions exacerbated by the physiologic changes of pregnancy. This article reviews obstetric disorders leading to intensive care unit admissions.

Venous thromboembolism in pregnancy

The purpose of this review is to summarize the epidemiology of venous thromboembolism (VTE) in pregnancy and describe strategies used to prevent and treat it. The main reason for the increased risk of VTE in pregnancy is hypercoagulability. The hypercoagulability of pregnancy, which has likely evolved to protect women from the bleeding challenges of miscarriage and childbirth, is present as early as the first trimester and so is the increased risk of VTE. Other risk factors include a history of thrombosis, inherited and acquired thrombophilia, certain medical conditions, and complications of pregnancy and childbirth. Candidates for anticoagulation are women with a current thrombosis, a history of thrombosis, thrombophilia, and a history of poor pregnancy outcome, or postpartum risk factors for VTE. For fetal reasons, the preferred agents for anticoagulation in pregnancy are heparins. There are no large trials of anticoagulants in pregnancy and recommendations are based on case series and the opinion of experts. Nonetheless, anticoagulants are believed to improve the outcome of pregnancy for women who have or have had VTE.

Pregnancy-associated thrombosis

The main reason for the increased risk of thromboembolism in pregnancy is hypercoagulability, which has likely evolved to protect women from the bleeding challenges of miscarriage and childbirth. Women are at a 4- to 5-fold increased risk of thromboembolism during pregnancy and the postpartum period compared with when they are not pregnant. Eighty percent of the thromboembolic events in pregnancy are venous, with an incidence of 0.49 to 1.72 per 1000 pregnancies. Risk factors include a history of thrombosis, inherited and acquired thrombophilia, maternal age greater than 35, certain medical conditions, and various complications of pregnancy and childbirth. Despite the increased risk of venous thromboembolism (VTE) during pregnancy and the postpartum period, most women do not require anticoagulation. Candidates include women with current VTE, a history of VTE, thrombophilia and a history of poor pregnancy outcome, or risk factors for postpartum VTE. The intensity of the anticoagulation will depend on the indication and the monitoring will depend on the intensity. At the time of delivery, anticoagulation should be manipulated to reduce the risk of bleeding complications while minimizing the risk of thrombosis. There are no large trials of anticoagulants in pregnancy, and recommendations are based on case series, extrapolations from nonpregnant patients and the opinion of experts. Nonetheless, anticoagulants are believed to improve the outcome of pregnancy for women who have, or have had, VTE.

Heparin-induced osteoporosis and pregnancy

PURPOSE OF REVIEW

Osteoporosis is the most common serious side effect of long-term unfractionated heparin use. Until recently, it was unknown whether long-term low-molecular-weight heparin was associated with any change in bone mineral density. With increasing long-term low-molecular-weight heparin use, for a variety of indications, this was an important knowledge gap.

RECENT FINDINGS

We recently completed an a-priori planned substudy to assess the effect of low-molecular-weight heparin on bone mineral density in an ongoing multicenter multinational randomized trial designed to compare the effect of low-molecular-weight heparin prophylaxis on pregnancy outcomes in thrombophilic pregnant women. The results revealed that there is no significant difference in mean bone mineral density between a low-molecular-weight heparin prophylaxis group and a no prophylaxis group. The study was not adequately powered to detect differences in absolute fracture risk.

SUMMARY

Recent results suggest that the use of long-term prophylactic low-molecular-weight heparin in pregnancy is not associated with a significant decrease in bone mineral density. Whether higher doses might be a risk factor for osteoporosis is still an unanswered question. It is also possible that subgroups are more susceptible. Overall, women should be reassured regarding the risk of osteoporosis associated with the use of prophylactic dose of low-molecular-weight heparin during their pregnancy.

Venous thromboembolism, thrombophilia, antithrombotic therapy, and pregnancy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This article discusses the management of venous thromboembolism (VTE) and thrombophilia, as well as the use of antithrombotic agents, during pregnancy and is part of the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that benefits do, or do not, outweigh risks, burden, and costs. Grade 2 recommendations are weaker and imply that the magnitude of the benefits and risks, burden, and costs are less certain. Support for recommendations may come from high-quality, moderate-quality or low-quality studies; labeled, respectively, A, B, and C. Among the key recommendations in this chapter are the following: for pregnant women, in general, we recommend that vitamin K antagonists should be substituted with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) [Grade 1A], except perhaps in women with mechanical heart valves. For pregnant patients, we suggest LMWH over UFH for the prevention and treatment of VTE (Grade 2C). For pregnant women with acute VTE, we recommend that subcutaneous LMWH or UFH should be continued throughout pregnancy (Grade 1B) and suggest that anticoagulants should be continued for at least 6 weeks postpartum (for a total minimum duration of therapy of 6 months) [Grade 2C]. For pregnant patients with a single prior episode of VTE associated with a transient risk factor that is no longer present and no thrombophilia, we recommend clinical surveillance antepartum and anticoagulant prophylaxis postpartum (Grade 1C). For other pregnant women with a history of a single prior episode of VTE who are not receiving long-term anticoagulant therapy, we recommend one of the following, rather than routine care or full-dose anticoagulation: antepartum prophylactic LMWH/UFH or intermediate-dose LMWH/UFH or clinical surveillance throughout pregnancy plus postpartum anticoagulants (Grade 1C). For such patients with a higher risk thrombophilia, in addition to postpartum prophylaxis, we suggest antepartum prophylactic or intermediate-dose LMWH or prophylactic or intermediate-dose UFH, rather than clinical surveillance (Grade 2C). We suggest that pregnant women with multiple episodes of VTE who are not receiving long-term anticoagulants receive antepartum prophylactic, intermediate-dose, or adjusted-dose LMWH or intermediate or adjusted-dose UFH, followed by postpartum anticoagulants (Grade 2C). For those pregnant women with prior VTE who are receiving long-term anticoagulants, we recommend LMWH or UFH throughout pregnancy (either adjusted-dose LMWH or UFH, 75% of adjusted-dose LMWH, or intermediate-dose LMWH) followed by resumption of long-term anticoagulants postpartum (Grade 1C). We suggest both antepartum and postpartum prophylaxis for pregnant women with no prior history of VTE but antithrombin deficiency (Grade 2C). For all other pregnant women with thrombophilia but no prior VTE, we suggest antepartum clinical surveillance or prophylactic LMWH or UFH, plus postpartum anticoagulants, rather than routine care (Grade 2C). For women with recurrent early pregnancy loss or unexplained late pregnancy loss, we recommend screening for antiphospholipid antibodies (APLAs) [Grade 1A]. For women with these pregnancy complications who test positive for APLAs and have no history of venous or arterial thrombosis, we recommend antepartum administration of prophylactic or intermediate-dose UFH or prophylactic LMWH combined with aspirin (Grade 1B). We recommend that the decision about anticoagulant management during pregnancy for pregnant women with mechanical heart valves include an assessment of additional risk factors for thromboembolism including valve type, position, and history of thromboembolism (Grade 1C). While patient values and preferences are important for all decisions regarding antithrombotic therapy in pregnancy, this is particularly so for women with mechanical heart valves. For these women, we recommend either adjusted-dose bid LMWH throughout pregnancy (Grade 1C), adjusted-dose UFH throughout pregnancy (Grade 1C), or one of these two regimens until the thirteenth week with warfarin substitution until close to delivery before restarting LMWH or UFH) [Grade 1C]. However, if a pregnant woman with a mechanical heart valve is judged to be at very high risk of thromboembolism and there are concerns about the efficacy and safety of LMWH or UFH as dosed above, we suggest vitamin K antagonists throughout pregnancy with replacement by UFH or LMWH close to delivery, after a thorough discussion of the potential risks and benefits of this approach (Grade 2C).

A descriptive evaluation of unfractionated heparin use during pregnancy

BACKGROUND

The mainstay of oral anticoagulant therapy, warfarin sodium, crosses the placenta during pregnancy and may cause fetal complications. Unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) do not cross the placenta and have demonstrated utility in the prevention and treatment of thrombosis during pregnancy.

OBJECTIVES

The purpose of this study was to review treatment strategy, indication, and maternal and fetal outcomes in anticoagulated pregnancies at Kaiser Permanente Colorado.

PATIENTS/METHODS

We identified 103 pregnancies in 93 mothers prescribed an anticoagulant during a pregnancy occurring between January 1, 1998 and March 31, 2005.

RESULTS

The majority of patients were treated with UFH (89.3%). Indications for anticoagulation included venous thromboembolism (VTE) prophylaxis (53.4%), history of pregnancy loss (29.1%), acute VTE (16.5%), and history of cerebral vascular accident (CVA) (1.0%). There were no maternal deaths. Fetal demise occurred in 8 pregnancies (7.8%) at a median 14 weeks gestation (range 7-22 weeks). No fetal demise occurred in pregnancies treated for acute VTE or history of CVA. There were two occurrences of pulmonary embolism (1.9%) and two hemorrhagic events requiring transfusion (1.9%).

CONCLUSIONS

Maternal and fetal adverse events were infrequent in our population of anticoagulated pregnancies. UFH remains a viable option among more expensive LMWH products.