Low molecular weight heparin in pregnancy: current issues

Prednisolone and enoxaparin (clexane) therapy ('the Bondi protocol') for repeated IVF failure

PROBLEM

What is the impact of an empirical immune therapy protocol of prednisolone and enoxaparin (clexane) (the 'Bondi protocol') on women with repeated in vitro fertilization (IVF) failure?

METHOD OF STUDY

This was a retrospective review of live birth outcomes conducted on all transfer cycles performed by a single clinician (GS) at IVFAustralia between February 2016 and April 2020. This study consisted of 1786 transfer cycles, including 460 cycles treated with the Bondi protocol and 1326 without. Women with repeated IVF failure were given the Bondi protocol based on blood NK cell activity. Primary outcome was live birth and statistical analysis was performed with GraphPad Prism software with significance for P-values < .05.

RESULTS

Overall 'Bondi' and 'normal' protocol cycles had similar rates of IVF/ICSI, fresh/frozen transfers and use of preimplantation genetic testing (PGT). Women given the Bondi protocol were older, had more previous cycles and had higher blood NK cell activity. There was no significant difference in live birth rates (Bondi 26%, normal 28%). Bondi protocol live birth rates per transfer cycle were as high as 40% in patients under 38 years old. The Bondi protocol was more effective as NK activity increased from 'normal' to 'borderline' to 'high'. For high NK cell activity levels, live birth rates were over four times higher for women on the Bondi protocol (28%) than those on normal protocols (6%, P = .0007).

CONCLUSION

This study describes a simple and relatively safe immune therapy protocol that may improve IVF success rates in women with evidence of immune dysfunction.

Heparin Protects Human Neural Progenitor Cells from Zika Virus-Induced Cell Death While Preserving Their Differentiation into Mature Neuroglial Cells

Zika virus (ZIKV) is an arbovirus member of the Flaviviridae family that causes severe congenital brain anomalies in infected fetuses. The key target cells of ZIKV infection, human neural progenitor cells (hNPCs), are highly permissive to infection that causes the inhibition of cell proliferation and induces cell death. We have previously shown that pharmaceutical-grade heparin inhibits virus-induced cell death with negligible effects on in vitro virus replication in ZIKV-infected hNPCs at the “high” multiplicity of infection (MOI) of 1. Here, we show that heparin inhibits formation of ZIKV-induced intracellular vacuoles, a signature of paraptosis, and inhibits necrosis and apoptosis of hNPCs grown as neurospheres (NS). To test whether heparin preserved the differentiation of ZIKV-infected hNPCs into neuroglial cells, hNPCs were infected at the MOI of 0.001. In this experimental condition, heparin inhibited ZIKV replication by ca. 2 log₁₀, mostly interfering with virion attachment, while maintaining its protective effect against ZIKV-induced cytopathicity. Heparin preserved differentiation into neuroglial cells of hNPCs that were obtained from either human-induced pluripotent stem cells (hiPSC) or by fetal tissue. Quite surprisingly, multiple additions of heparin to hNPCs enabled prolonged virus replication while preventing virus-induced cytopathicity. Collectively, these results highlight the potential neuroprotective effect of heparin that could serve as a lead compound to develop novel agents for preventing the damage of ZIKV infection on the developing brain.

IMPORTANCE ZIKV is a neurotropic virus that invades neural progenitor cells (NPCs), causing inhibition of their proliferation and maturation into neurons and glial cells. We have shown previously that heparin, an anticoagulant also used widely during pregnancy, prevents ZIKV-induced cell death with negligible inhibition of virus replication. Here, we demonstrate that heparin also exerts antiviral activity against ZIKV replication using a much lower infectious inoculum. Moreover, heparin interferes with different modalities of virus-induced cell death. Finally, heparin-induced prevention of virus-induced NPC death allows their differentiation into neuroglial cells despite the intracellular accumulation of virions. These results highlight the potential use of heparin, or pharmacological agents derived from it, in pregnant women to prevent the devastating effects of ZIKV infection on the developing brain of their fetuses.

Prognostic analysis of antibody typing and treatment for antiphospholipid syndrome-related recurrent spontaneous abortion

OBJECTIVE

To determine the efficacy of antibody typing and treatment on live birth rate in Chinese patients with antiphospholipid syndrome (APS)-related recurrent spontaneous abortion (RSA).

METHODS

A retrospective study analyzed 4542 Chinese patients who experienced spontaneous abortion, of whom 314 had APS (272 primary and 42 secondary). Type of antibodies was tested. Anticoagulant and anti-inflammatory treatments were adopted according to the titer and type of antibodies. The incidence of repeated abortion and placental dysfunction, gestational age, and mean weight of the fetuses were recorded.

RESULTS

Among the patients with APS-related RSA, primary APS accounted for the largest proportion. The proportion of antibody classification was as follows: β2-glycoprotein 1 (β2GP1)-IgM (151, 48.08%), lupus anticoagulant (LAC) (36, 11.46%), anticardiolipin (aCL)-IgM (32, 10.19%), β2GP1-IgM and aCL-IgM (29, 9.23%), and aCL-IgG (16, 5.09%). After treatment, the negative conversion of antibody, including β2GP1-IgM and LAC, significantly improved pregnancy outcomes. There was no significant difference in pregnancy outcomes between the other antibody titers.

CONCLUSION

The combination of anticoagulant and anti-inflammatory treatment led to a higher live birth rate in the treatment of APS-related RSA, highlighting the potential of antibody typing in providing clinical guidance for the treatment of APS-related RSA.

Current opinion and emerging trends on the treatment, diagnosis, and prevention of pregnancy-associated venous thromboembolic disease: a review

Pregnancy associated venous thromboembolism (PA-VTE) is a leading cause of maternal morbidity and mortality worldwide. Despite the availability of international guidance on the prevention, diagnosis and treatment, practice differs between countries and clinical institutions. The evidence base in this area is limited due to the vulnerable population who are affected, with the majority of guidelines deriving their recommendations from experience in surgical and medical venous thromboembolic disease. This review includes best evidence in PA-VTE management, highlighting specific literature which supports current diagnosis, prevention, and treatment strategies. Additionally, we hope to demonstrate emerging trends in the field through discussion of ongoing trials designed to progress towards evidence-based practice in the context of PA-VTE.

Factors associated with women's adherence to postpartum thromboprophylaxis

Postpartum low-molecular-weight heparin (LMWH) thromboprophylaxis is indicated for a substantial proportion of women. We assessed women's adherence to postpartum thromboprophylaxis and the factors associated with adherence. This retrospective cohort study was conducted at a university hospital during 2018. Parturients for whom a recommendation for LMWH prophylaxis was given at discharge from the maternity ward were contacted at the end of the recommended post-discharge course of LMWH, and were invited to participate in a telephone survey. The main outcome measures were optimal (> 80%) and suboptimal adherence (< 80%) to LMWH administration, reasons for nonadherence, and views regarding LMWH, as assessed by an adapted Beliefs about Medication Questionnaire. Overall, 250 women completed the questionnaire. The median recommended duration of post-discharge LMWH was 7 [5-8] days. Suboptimal adherence was reported by 82 (32.8%); 45 (18.0%) women did not administer any LMWH dose following discharge and only 147 (58.8%) completed the full LMWH course. In multivariate analysis, patients' perceptions of the necessity of LMWH [odds ratio (95% CI): 3.50 (2.12, 9.53), P = 0.002] and of the adequacy of the explanation given prior to discharge regarding LMWH technical administration [odds ratio (95% CI): 5.0 (2.33, 11.11), P < 0.001] were positively associated with optimal adherence. Nearly one-third of women prescribed postpartum LMWH thromboprophylaxis reported suboptimal adherence. Patients' perceptions of the necessity of the treatment and their opinion of the adequacy of explanation regarding LMWH technical administration were identified as predictors of treatment compliance, and thus represent potential areas for improvement.

Heparin prevents oxidative stress-induced apoptosis in human decidualized endometrial stromal cells

Clinical trials have shown that administering heparin during the luteal phase has beneficial effects on implantation and live birth rates. Heparin exerts direct effects on decidual human endometrial stromal cells (HESCs), which are independent of its anticoagulant effect. However, the accurate effects of heparin on the decidualization process remain unidentified. Here, we demonstrate that HESCs become dramatically resistant to oxidative stress upon decidualization, and we hypothesize a possible direct action of heparin on the decidualization of HESCs, which would lead to improved implantation. To test this hypothesis, we established primary HESC cultures and propagated them, and then we decidualized confluent cultures with 8-bromo-cAMP, with medroxyprogesterone acetate, and with or without heparin. We treated the cells with hydrogen peroxide (H₂O₂) as a source of reactive oxygen species (ROS). Adding heparin to decidualized HESCs induced prolactin secretion. Decidualized HESCs treated with heparin were prevented from undergoing apoptosis induced by oxidative stress. Heparin induced nuclear accumulation of the forkhead transcription factor FOXO1 and expression of its downstream target, the ROS scavenger superoxide dismutase 2. These results demonstrate that heparin-treated decidualized HESCs acquired further resistance to oxidative stress, suggesting that heparin may improve the implantation environment.

Adjustment of therapeutic LMWH to achieve specific target anti-FXa activity does not affect outcomes in pregnant patients with venous thromboembolism

Venous thromboembolism (VTE) remains a leading cause of maternal morbidity and mortality in the developed world. Low molecular weight heparins (LMWH) are routinely used to provide therapeutic anticoagulation during pregnancy for women with VTE, with measurement of plasma anti-FXa activity used to guide dosing in certain patient groups. There is limited evidence to support the use of anti-FXa monitoring in pregnant patients. This study seeks to ascertain whether anti-FXa monitoring of pregnant patients with VTE influences patient outcomes. We performed a single-centre case series including two consecutive groups of pregnant patients treated with LMWH for VTE sustained in the index pregnancy with and without monitoring of anti-FXa levels. 35,394 patients delivered during the study period in a large urban stand-alone maternity hospital, with 26 cases of VTE eligible for inclusion. There was no significant difference between the two groups in any clinical outcome; including maternal blood loss at delivery, recurrent thromboembolic events or rates of planned delivery. These data provide clinical evidence to support current international guideline recommendations that measurement of plasma anti-FXa activity in the majority of patients receiving therapeutic-intensity antenatal LMWH is not warranted.

Birthweight in pregnant women with protein S deficiency treated with low-molecular-weight heparin: a retrospective cohort study

OBJECTIVE

To determine the risk of small-for-gestational-age (SGA) and intrauterine growth retardation (IUGR) in pregnant women with protein S (PS) deficiency who received low-molecular-weight heparin (LMWH).

METHODS

Retrospective cohort study of pregnant women seen from January 2002 to December 2011. The study cohort comprised a total of 328 patients with PS deficiency, who received prophylactic enoxaparin during pregnancy. The control cohort included 11 884 pregnant women without significant past medical history. The risk of SGA and IUGR was calculated as odds ratio. Multivariate regression analysis over the entire reference population was performed determining the risk of both SGA and IUGR by adjusting for maternal age, first delivery, maternal underweight status, pre-eclampsia, other treated thrombophilias or history of recurrent abortion.

RESULTS

The SGA rates in the PS deficiency and control cohorts were 10.7% and 8.5%, respectively (p > 0.05). There was no increased risk of SGA (unadjusted OR = 1.28, 95% confidence interval [CI] 0.9-1.83; adjusted OR = 1.35, 95% CI 0.91-2.01). The IUGR rate was 2.7% in pregnant women with PS deficiency versus 4.1% in the control group (p > 0.05). Also, we did not find a significant risk of IUGR (OR = 0.66; 95% CI 0.34-1.28; adjusted OR = 0.843; 95% CI 0.42-1.70).

CONCLUSIONS

In women with PS deficiency treated with LMWH, the risk of SGA and IUGR is similar to the one found in healthy pregnant women.

Enoxaparin Use in Pregnancy: State of the Art

Low-molecular-weight heparin is the anticoagulant of choice in pregnancy. Enoxaparin has been increasingly used over the past 20 years in pregnant women at risk of thrombosis and pregnancy complications. The main indications are prophylaxis of venous thromboembolism and prevention of pregnancy loss in thrombophilic women. Other indications include treatment of venous thromboembolism, prophylaxis of arterial thrombosis in pregnant women with mechanical heart valves and prevention of late gestational complication such as pre-eclampsia and intrauterine growth restriction. Enoxaparin does not cross the placenta and is safe for the fetus. Maternal side effects are uncommon and include mild localized allergic reactions in 2% and increased bleeding in 2%, which is dose dependent. Heparin-induced thrombocytopenia is very rare and bone resorption is not clinically relevant. The mechanisms of action of enoxaparin in pregnancy are multiple and include anti-factor Xa (anti-Xa) activity in maternal circulation, tissue factor pathway inhibitor release from endothelial cells and trophoblasts at the placental level as well as anti-inflammatory effects.

Pharmacology of Heparin and Related Drugs

Heparin has been recognized as a valuable anticoagulant and antithrombotic for several decades and is still widely used in clinical practice for a variety of indications. The anticoagulant activity of heparin is mainly attributable to the action of a specific pentasaccharide sequence that acts in concert with antithrombin, a plasma coagulation factor inhibitor. This observation has led to the development of synthetic heparin mimetics for clinical use. However, it is increasingly recognized that heparin has many other pharmacological properties, including but not limited to antiviral, anti-inflammatory, and antimetastatic actions. Many of these activities are independent of its anticoagulant activity, although the mechanisms of these other activities are currently less well defined. Nonetheless, heparin is being exploited for clinical uses beyond anticoagulation and developed for a wide range of clinical disorders. This article provides a "state of the art" review of our current understanding of the pharmacology of heparin and related drugs and an overview of the status of development of such drugs.

Surgical treatment of melanoma in pregnancy: a practical guideline

A tumor primarily requiring surgical treatment, newly diagnosed or preexisting melanoma during pregnancy is a clinical rarity. In such cases, the surgeon faces the challenge of having to decide on the appropriate therapeutic course of action. Based on our clinical experience and a review of the literature, we herein provide a guideline on how to practically deal with this rare clinical conundrum. In our experience, pregnant melanoma patients require thorough counseling with respect to their therapeutic options. They naturally tend to put their unborn child first, and are hesitant to consent to necessary surgery despite a potentially life-threatening diagnosis. It is therefore crucial to clearly inform these patients that - based on existing medical experience - pregnancy by itself is no reason to hold off on any type of necessary melanoma surgery. However, various parameters such as preoperative imaging procedures, positioning on the operating table, monitoring, anesthesia, and perioperative medication require certain adjustments in order to comply with this special situation.

Chirurgische Behandlung von Melanomen in der Schwangerschaft: eine praktische Anleitung

Als ein Tumor, der primär eine chirurgische Behandlung erfordert, ist ein neu diagnostiziertes oder vorbestehendes Melanom in der Schwangerschaft eine klinische Rarität. In solchen Fällen steht der Chirurg vor der Herausforderung, ein geeignetes therapeutisches Vorgehen festlegen zu müssen. Auf der Grundlage unserer klinischen Erfahrung und einer Übersicht über die Literatur geben wir in der vorliegenden Arbeit eine Anleitung für das praktische Vorgehen bei dieser seltenen klinischen Konstellation. Unserer Erfahrung nach müssen schwangere Melanom-Patientinnen im Hinblick auf ihre therapeutischen Optionen ausführlich beraten werden. Naturgemäß setzen sie ihr ungeborenes Kind an die erste Stelle und zögern, der erforderlichen Operation zuzustimmen, obwohl bei ihnen eine möglicherweise lebensbedrohliche Erkrankung diagnostiziert worden ist. Daher ist es entscheidend, diese Patientinnen klar darüber zu informieren, dass, wie die vorliegenden medizinischen Erfahrungen zeigen, eine Schwangerschaft per se kein Grund ist, eine notwendige Melanom-Operation aufzuschieben. Jedoch müssen bei einigen Parametern wie den präoperativen Bildgebungsverfahren, der Positionierung auf dem Operationstisch, der Überwachung, Anästhesie und der perioperativen Medikation bestimmte Anpassungen vorgenommen werden, um der speziellen Situation Rechnung zu tragen.

The presence of heparins during decidualization modulates the response of human endometrial stromal cells to IL-1β in vitro

PURPOSE

The aim of this paper is to study the impact of heparin on the response of human endometrial stromal cells (ESCs) to interleukin (IL)-1β during decidualization in vitro.

METHODS

ESCs were isolated from hysterectomy specimens of premenopausal women undergoing hysterectomy for benign reasons; decidualized in vitro and incubated in parallel with unfractionated heparin or tinzaparin; and stimulated with IL-1β at days 0, 3, 6, and 9 during decidualization. IL-6, IL-11, and leukemia inhibitory factor (LIF) were analyzed using ELISAs and real-time RT-PCR. Cell viability was determined by a fluorometric assay.

RESULTS

IL-1β dose-dependently stimulated IL-6, IL-11, and LIF in distinct patterns in ESCs during decidualization. Unfractionated heparin as well as tinzaparin attenuated the IL-1β-mediated induction of IL-6, IL-11, and LIF on protein and messenger RNA (mRNA) levels. The relative effects of heparin and tinzaparin were getting more pronounced during the time course of decidualization.

CONCLUSIONS

Unfractionated heparin and the low molecular weight heparin tinzaparin have modulating effects on IL-1β-induced endometrial cytokines of the IL-6 family during decidualization. These effects of heparins beyond their classical anti-coagulatory properties might have implications on the regulation of endometrial receptivity and early implantation.

Prothrombotic state of patients with unexplained recurrent spontaneous abortion

OBJECTIVE

To determine the effect of aspirin and low-molecular-weight heparin (LMWH) for women affected by recurrent spontaneous abortion (RSA).

METHODS

The present prospective observational study included women with RSA (≥ 2 previous spontaneous abortions) and those without a history of RSA attending Ren Ji Hospital, Shanghai, China, between March 2011 and March 2014. D-dimer levels, auto-antibodies, and platelet aggregation in response to arachidonic acid (AA) and adenosine diphosphate (ADP) were monitored before pregnancy. Women with unexplained RSA and increased platelet aggregation received low-dose aspirin, and those with elevated D-dimer levels (> 0.75 μg/mL) received LMWH. Platelet aggregation in response to AA and ADP, and D-dimer levels were monitored during pregnancy.

RESULTS

Among 517 participants with RSA, 325 had unexplained RSA. Compared with 63 control patients, those with unexplained RSA and two, three, four, or at least five previous spontaneous abortions had increased platelet aggregation in response to AA (P < 0.05 for all comparisons) but not to ADP. Among 37 women with unexplained RSA who became pregnant, aspirin reduced platelet aggregation in response to AA (P < 0.001). LMWH reduced D-dimer levels during pregnancy (P < 0.001). Among 37 women with unexplained RSA who became pregnant and completed the study, 33 (89.2%) had a live birth.

CONCLUSION

Aspirin and LMWH maintained a lower thrombotic state and led to a high live birth rate among patients with unexplained RSA.

Pulmonary embolism: current and new treatment options

BACKGROUND

Pulmonary embolism (PE) can be a life-threatening emergency. Accurate diagnostic techniques and patient-specific management strategies are necessary to ensure favorable clinical outcomes.

METHODS

Relevant guidelines, articles, reviews, and abstracts were identified using a narrative approach in PubMed/MEDLINE, Google Scholar, clinicaltrials.gov and nice.org.uk. English-language articles published in 2000-2014 were initially identified using the search terms: novel OAC, pulmonary embolism, venous thromboembolism, diagnosis, treatment, rivaroxaban, apixaban, dabigatran, and edoxaban. The initial literature search was supported by a 'snowballing' style literature search, and relevant articles were included based on a professional judgment of relevance.

SCOPE

We discuss the diagnosis of PE and the categorization of risk for subgroups, which may assist with making treatment decisions. We review current guidance on acute and long-term treatment, possible limitations of traditional anticoagulant therapy, and the development of direct oral anticoagulants, which may significantly alter the management of patients with PE. Finally, we discuss special considerations in high-risk and hard-to-treat subpopulations that may benefit from the improved benefit-risk profile offered by these newer agents.

CONCLUSIONS

The direct oral anticoagulants may overcome several of the limitations associated with traditional anticoagulant therapy, potentially improving the standard of care for PE patients, including high-risk and hard-to-manage subgroups.

Anticoagulation in pregnant patients with mechanical heart valves: clinical considerations

Pregnancy management with mechanical heart valves is best done collaboratively with experienced cardiologists and maternal fetal medicine specialists. All anticoagulation options are associated with risks and benefits. Pregnancy is one situation in which the benefit of warfarin use may outweigh the risks. In light of the absence of definitive research to suggest a superior regimen, the risks, benefits, and limitations of each strategy should be discussed with the patient and specific attention given to her individual clinical situation.

Thrombosis in pregnancy: updates in diagnosis and management

Acute venous thromboembolism poses significant problems in pregnancy, a time when objective diagnosis and prompt treatment are essential. Events can occur at any stage in pregnancy, but the period of greatest risk is in the weeks after delivery. Ultrasound venography remains the diagnostic technique of choice for deep venous thrombosis. For pulmonary thromboembolism, ventilation perfusion lung scan is usually preferred more than computerized tomography pulmonary angiography because of the lower maternal radiation dose and the lower prevalence of coexisting pulmonary problems. Low-molecular-weight heparin is the agent of choice for treatment of venous thromboembolism in pregnancy, and treatment should be provided for a minimum of 3 months and for at least 6 weeks after delivery. New anticoagulant agents such as dabigatran, rivaroxaban, or apixaban are not recommended for use in pregnancy.

Women's views on and adherence to low-molecular-weight heparin therapy during pregnancy and the puerperium

BACKGROUND

Non-adherence to prescribed medication represents a significant factor associated with treatment failure. Pregnant women identified at risk of venous thromboembolism are increasingly being prescribed low-molecular-weight heparin (LMWH) during pregnancy and the puerperium. It is important to understand women's views on and adherence to LMWH during pregnancy and the puerperium, so that women gain maximum benefit from the treatment.

OBJECTIVES

To monitor women's adherence to enoxaparin, when prescribed during pregnancy and the puerperium, and explore their beliefs about the enoxaparin therapy prescribed.

PATIENTS/METHODS

A prospective cohort study involving 95 nullparous and multiparous women prescribed enoxaparin for recognized antenatal indications. Adherence to enoxaparin was assessed through self-completion of a diary, additionally verified through laboratory tests. An adapted beliefs about medication questionnaire was administered to women during their pregnancy.

RESULTS

Women were highly adherent to enoxaparin: antenatally, mean percentage adherence 97.92%; postnatally, mean percentage adherence 93.37% (paired t-test, P = 0.000). In the cohort of women we followed, their perceived necessity for enoxaparin therapy outweighed any concerns they had regarding enoxaparin antenatally, necessity-concerns differential 2.20. In some women, however, this perceived necessity does decrease postnatally.

CONCLUSIONS

Our results suggest that most women prescribed enoxaparin are highly adherent to their therapy during the antenatal period and that women's antenatal beliefs about enoxaparin are able to predict a decrease in postnatal adherence. Our results have important clinical implications, particularly when women are initiated on LMWH just during the postnatal period.

Pregnancy-associated venous thrombosis

Pregnant women are at an increased risk of venous thromboembolism (VTE) and the consequences of an acute event in pregnancy can be debilitating, long-lasting or fatal. Screening for risk factors early in pregnancy and the provision of thromboprophylaxis are useful ways of preventing VTE in some women, but even when performed diligently, acute events are likely to remain common for the foreseeable future. It is therefore important for obstetric and non-obstetric clinicians to recognize the symptoms and signs of deep vein thrombosis and pulmonary embolism in pregnancy, to understand how a diagnosis can be reached in an effective yet safe manner and to be aware of the available treatment modalities.

Leveraging physiological data from literature into a pharmacokinetic model to support informative clinical study design in pregnant women

PURPOSE

Physiological changes during pregnancy can effect pharmacokinetic (PK) parameters, which may lead to altered dose requirements. We aimed to leverage literature-based physiological changes during pregnancy into a PK model and compare its performance to a published reference model in pregnant women and to use the literature-based model to determine informative PK sampling times for a clinical study that aims to quantify the PK of enoxaparin throughout pregnancy.

METHODS

Changes in total body water (BW) and creatinine clearance (CRCL) during pregnancy were described using regression models. BW and CRCL were linked to a PK model of enoxaparin in non-pregnant women. Performance of the literature-based PK model was compared to a previously published empirical reference model. D-optimal sampling times were determined and evaluated for literature-based and reference models.

RESULTS

The literature-based model adequately predicted anti-Xa plasma concentrations when compared to reference model predictions. An informative sampling design was successfully developed, with parameters expected with good precision (RSE < 36.4%).

CONCLUSION

A literature-based model describing enoxaparin PK during pregnancy was developed and evaluated. The modelling framework could be used to support development of informative designs in pregnancy when prior models are unavailable.

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.

Diagnosis and treatment of deep-vein thrombosis and approach to venous thromboembolism in obstetrics and gynecology

Deep vein thrombosis (DVT) is a common condition in which the approach to its diagnosis has evolved over the years. Currently, an algorithm strategy combining pre-test probability, D-Dimer testing and compression ultrasound imaging allows for safe and convenient investigation of suspected lower-extremity thrombosis. Patients with low pre-test probability and a negative D-Dimer test result can have proximal DVT excluded without the need for diagnostic imaging. The mainstay of treatment of DVT is anticoagulation therapy, whereas interventions such as thrombolysis and placement of inferior vena cava filters are reserved for special situations. The use of low-molecular-weight heparin (LMW) allows for outpatient management of most patients with DVT. The duration of anticoagulation therapy depends on whether the primary event was idiopathic or secondary to a transient risk factor. More research is required to optimally define the factors that predict an increased risk of recurrent DVT to determine which patients can benefit from extended anticoagulant therapy. DVT is also a serious problem in the antenatal and postpartum period of pregnancy. Thromboembolic complications are the leading cause of both maternal and fetal morbidity and mortality. The incidence of venous thromboembolism during normal pregnancy is six-fold higher than in the general female population of childbearing age. The treatment of DVT during pregnancy deserves special mention, since oral anticoagulation therapy is generally avoided during pregnancy because of the teratogenic effects in the first trimester and the risk of fetal intracranial bleeding in the third trimester. LMW heparin is the treatment of choice for DVT during pregnancy. If acute DVT occurs near term, interrupting anticoagulation therapy may be hazardous because of the risk of pulmonary embolism. In this situation, placement of a retrievable inferior vena cava filter must be considered. However, there is no consensus as to what the appropriate dose should be and whether anti-Xa levels need to be monitored.

Anticoagulant and antithrombotic drugs in pregnancy: what are the anesthetic implications for labor and cesarean delivery?

Neuraxial anesthetic techniques are commonly used during the peripartum period to provide effective pain relief for labor and anesthesia during cesarean delivery. Major neurologic complications are rare after neuraxial anesthesia; however, spinal hematoma is associated with catastrophic neurologic outcomes (including lower-limb paralysis). Anticoagulant and antithrombotic drugs can increase the risk of spinal hematoma after neuraxial anesthesia, and better understanding of the pharmacokinetics and pharmacodynamics of anticoagulants has led to greater appreciation for withholding anticoagulation before and after neuraxial anesthesia. A number of national anesthetic societies have produced guidelines for performing neuraxial anesthesia in patients receiving anticoagulation. However, there is limited information about anesthetic implications of anticoagulation during the peripartum period. This article will review the risks of spinal hematoma after neuraxial anesthesia in pregnant patients; current guidelines for neuraxial anesthesia for anticoagulated patients; and relevant pharmacological data of specific anticoagulant and antithrombotic drugs in pregnancy.

HEPARIN IN HUMAN PLACENTAL DEVELOPMENT AND THE PREVENTION OF PLACENTAL COMPLICATIONS OF PREGNANCY

The development of effective anticoagulant drugs available for use in pregnancy has resulted in dramatic improvements for a number of potentially life-threatening conditions. These include the treatment and prevention of venous thromboembolism and the thrombotic complications of antiphospholipid antibody syndrome, as well as the management of pregnant women with mechanical heart valves. The most commonly used class of drug includes heparin, a highly-charged macro-molecule that does not cross the placenta, in contrast to the potentially teratogenic and fetotoxic oral drug warfarin. This review will focus on our current lack of understanding of the wider actions of heparin and examines the possibility that large numbers of pregnant women are presently being treated inappropriately with heparin.

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.

The effects of antenatal anticoagulants (low-molecular-weight heparin and aspirin) on neonatal pulmonary vasculature in rabbits

Low-molecular-weight heparin and aspirin are the most prescribed medical agents as anticoagulants in pregnancy. Our objective was to investigate the effects of antenatal use of low-molecular-weight heparin and aspirin on pulmonary vascular development in neonatal rabbits. Seven pregnant rabbits (42 newborn rabbits) were divided into 5 groups as follows: control group (group 1, n = 14), heparin treated (group 2, n = 8), heparin and aspirin treated (group 3, n = 7), only aspirin treated (group 4, n = 6), and high-dose heparin treated (group 5, n = 12). Pulmonary histologic evaluations were carried out for all groups. Angiogenesis was also tested by CD34 immunostained microvessel count (mvc). Pathologic examination of pulmonary vasculature revealed that pulmonary vascular thickening occurred at the level of alveoli in heparin-, heparin- and aspirin-, and high-dose-heparin-treated groups (groups 2, 3, and 5). The percentage of wall thickness was different in groups 2 (26%), 3 (28.2%), and 5 (30.8%) compared with group 1 (21.4%). Statistical differences were observed between group 1 vs 2, 3, and 5. Microvessel count was also different between groups 2 (mvc = 90.5), 3 (mvc = 90.2), and 5 (mvc = 96.3) vs group 1 (mvc = 86.7). The microvessel count was statistically different between groups that received low-dose heparin vs high-dose heparin. Antenatal administration of low-molecular-weight heparin showed an effect on pulmonary vascular development. This effect may be explained by the influence of heparin on angiogenesis through placental growth factors. Further experiments are needed to understand the pathophysiology of these findings, and clinical studies are needed to correlate of these results.

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.

Inherited Thrombophilia

Inherited thrombophilia can be defined as a genetically determined predisposition to the development of thromboembolic complications. Since the discovery of activated protein C resistance in 1993, several additional disorders have been described and, at present, it is possible to identify an inherited predisposition in about 60 to 70% of patients with such complications. These inherited prothrombotic risk factors include qualitative or quantitative defects of coagulation factor inhibitors, increased levels or function of coagulation factors, defects of the fibrinolytic system, altered platelet function, and hyperhomocysteinemia. In this review, the main inherited prothrombotic risk factors are analyzed from epidemiological, laboratory, clinical, and therapeutic points of view. Finally, we discuss the synergism between genetic and acquired prothrombotic risk factors in particular conditions such as childhood and pregnancy.

Where do we go now with low molecular weight heparin use in obstetric care?

The use of low molecular weight heparins (LMWH) in obstetric care has grown considerably since their introduction into clinical practice in the early 1990s. However, because of the physiological changes of pregnancy, the predictable pharmacokinetic profile of LMWH is lost and some uncertainty exists around the optimal dosing regimen for LMWH in obstetric care. Two recent United Kingdom prospective surveys of the management of acute venous thromboembolism (VTE) suggest that despite recommendations from the Royal College of Obstetricians and Gynaecologists (RCOG) for a twice daily LMWH regimen, a once daily regimen is acceptable for the treatment of venous thromboembolism; and that accepted thromboprophylactic doses licensed for non-pregnant individuals may not be applicable during the second and third trimester for VTE thromboprophylaxis. Accepting that randomized clinical studies are difficult in obstetric care, future advances could be made through population-based multi-center studies, coupled with pharmacokinetic modeling studies, which have the potential to determine the optimal dosing regimen for the various obstetric indications.

Management of pregnant women with cardiac diseases at potential risk of thromboembolism--experience and review

Over a 7-year period, the chart records of six pregnant women with cardiac diseases at potential risk of thromboembolism were reviewed. All six patients survived and recovered well eventually. LMWH and beta-adrenergic blocker were effective to deal with atrial fibrillation. Digitalis and dobutamine were beneficial to prevent heart failure resulted from degenerated porcine valve and dilated cardiomyopathy. In a patient with mechanical mitral valve, low-dose warfarin did not cause fetal malformation, and was effective to prevent thrombus formation. Protamine sulfate was safely administered to neutralize intravenous heparin effect before vaginal delivery. Life-threatening postpartum pulmonary hemorrhage occurred as a result of pulmonary hypertension with an aberrant right pulmonary artery, absolutely necessitating a long-term cardiopulmonary bypass resuscitation. Patient with primary pulmonary hypertension gave birth safely with forceps assistance under epidural anesthesia. From literatures reviewed and successful experiences presented here, prenatal correction of the underlying cardiac malformation, precise switch of anticoagulant administration, optimizing cardiac function, early delivery prior to heart failure, postpartum fluid restriction, minimized peripartum blood loss, and meticulously intensive cares are essential to achieve satisfactory outcomes.

Maternal morbidity, mortality, and risk assessment

Maternal deaths in developed countries continue to decline and are rare. Maternal mortality statistics are essentially similar in the United States and United Kingdom. However, the situation is completely different in developing countries, where maternal mortality exceeds 0.5 million every year. This article not only assesses morbidity risks in some of the leading causes of maternal death but also highlights strategies to minimize the risks and to prevent maternal morbidity and mortality.

Pharmacokinetics, efficacy, and safety of LMWHs in venous thrombosis and stroke in neonates, infants and children

Since the early nineties it has been shown that low molecular weight heparin (LMWH) has significant advantages over unfractionated heparin and oral anticoagulants for both the treatment and the prevention of thrombosis, not only in adults, but also in children. The present review was based on an 'EMBASE', 'Medline' and 'PubMed' search including literature published in any language since 1980 on LMWH in neonates, infants and children. It included paediatric pharmacokinetic studies, the use of LMWH in children with venous thrombosis, LMWH administration in paediatric patients with ischaemic stroke, and its use in order to prevent symptomatic thromboembolism in children at risk. An increasing rate of off-label use of LMWH in children has been reported, showing that LMWHs offer important benefits to children with symptomatic thromboembolic events and poor venous access. Two well-conducted pharmacokinetic studies in this age group showed that neonates and younger infants require higher LMWH doses than older children to achieve the targeted anti-Xa levels, due to an increased extra vascular clearance. Recurrent symptomatic thromboses under LMWH occur in approximately 4% of children treated for venous thrombosis, and in 7% of children treated for stroke; major bleed was documented in 3% of children with therapeutic target LMWH anti-Xa levels, whereas minor bleeding was reported in approximately 23% of children receiving either therapeutic or prophylactic doses, respectively. Further randomized controlled trials are recommended to evaluate the optimum duration and application for different LMWH indications in children.