Prothrombin and factor V mutations in women with a history of thrombosis during pregnancy and the puerperium

Venous Thromboembolism Prophylaxis in Obstetric Patients

Venous thromboembolism (VTE), including both pulmonary embolism (PE) and deep vein thrombosis (DVT), is the leading cause of maternal death in developed countries. Pregnancy is associated with an increased risk of VTE due to physiologic changes during the obstetric period that promote a hypercoagulable state. Appropriate use of prophylactic anticoagulants can decrease the event rate of thrombus formation in at-risk patients. In the United States, there is not a validated risk-assessment tool for VTE in obstetric patients or a clear consensus on initiation and optimal dosing strategy for the prophylactic use of anticoagulants. This article reviews the mechanism of coagulation disturbance that leads to an increased risk of VTE in obstetric patients, as well as the available literature surrounding pharmacologic prophylaxis.

Diagnosis and treatment of venous thromboembolism during pregnancy relate to genetic polymorphism

OBJECTIVES

Previous research had shown that age, a positive family history, comorbidities, major surgical operations, gestation, and use of several medications could increase the incidence of venous thromboembolism (VTE). With the development of medical and clinical individualized treatment, many people exposed to above risk factors did not develop VTE, suggested that genetic factors are also involved in the development of VTE. In this review, we aim to summarize VTE diagnosis and treatment in pregnancy women related to gene polymorphism.

METHODS

A comprehensive electronic search using PubMed, MEDLINE, EMBASE and Web of Science was conducted to find relevant journal articles with key search terms including: "pregnancy OR pregnant," "venous thromboembolism OR VTE," "deep vein thrombosis OR DVT," "pulmonary embolism OR PE," and "genetic OR gene." Prominent publications from establishment of database till present were analysed to achieve a deeper understanding of VTE during pregnancy relate to genetic polymorphism, and the information was then collated to form this review.

RESULTS

The literature review revealed that inherited thrombophilia significantly associated with the development of VTE, especially the factor V Leiden (FVL) and prothrombin gene mutation (PGM). Furthermore, the role of methylenetetrahydrofolate reductase (MTHFR) gene mutation in the development of pregnancy-related VTE remains controversial, further study is required. In the present study, Marburg I polymorphism (G511 E), c.1538 G>A and c.1601 G>A in Factor V (FV), JAK2V617 F mutation were reported as an independent risk factor for VTE, there is no sufficient evidence to confirm the gene mutation is related to VTE during pregnancy, these factors appearing as another promising potential diagnostic marker of VTE during pregnancy. Besides, the dosages of heparin in the treatment of VTE during pregnancy need be adjusted according to gene polymorphism of these population, particularly FVL or PGM carriers, and this area is not studied deeply, it is worth further study.

CONCLUSION

Inherited thrombophilia significantly associated with the development of VTE, especially the FVL and PGM, however the relation between MTHFR gene mutation and pregnancy-related VTE remains controversial, further study is needed. In addition, the dosages of heparin in the treatment of VTE during pregnancy suggested to adjusted based on gene polymorphism in FVL and PGM, and establish better prediction models is a direction of future research.

To Test or Not to Test: Routine Thrombophilia Diagnostic Screening of Women with Reproductive Failures

BACKGROUND

Recurrent reproductive failure is a global health issue affecting a significant number of women. Thrombophilias have been implicated as a possible cause. Inherited thrombophilias include a single nucleotide variant on factor V Leiden and prothrombin.

OBJECTIVE

The aim of this study was to evaluate the association between the following single nucleotide variants: factor V Leiden (c.1601G>A), the prothrombin gene (c.*97G>A) and the reproductive failure in the Polish population.

METHODS

The study was conducted in a group of 545 patients with recurrent pregnancy loss, RPL (≥2 miscarriages), and in a group of 641 patients with infertility. The distribution of genotypes for the selected variants were determined by RFLP-PCR and by the real-time PCR method.

RESULTS

A variant of the F5 gene was found in 5.14% of patients with RPL and in 6.08% of infertile women. A variant of the F2 gene was identified in 0.73% of patients with RPL and in 2.03% of women with infertility. The frequency in the study groups did not differ from that in the general population. No association between the studied variants of the F5 gene or the F2 gene and the predisposition to reproductive wastage was found.

CONCLUSIONS

Recommendations for routine thrombophilia testing in women with recurrent miscarriages should be revisited. The decision regarding testing should be made individually depending on additional factors indicating an increased risk of venous thromboembolism.

A erythrocyte-platelet hybrid membrane coated biomimetic nanosystem based on ginsenosides and PFH combined with ultrasound for targeted delivery in thrombus therapy

Thrombus is one of the culprits for global health problems. However, most current antithrombotic drugs are limited by restricted targeting ability and a high risk of systemic bleeding. A hybrid cell membrane-coated biomimetic nanosystem (PM/RM@PLGA@P/R) was constructed in this paper to fulfil the targeted delivery of ginsenoside (Rg1) and perfluorohexane (PFH). Poly lactic-co-glycolic acid (PLGA) is used as carriers to coat Rg1 and PFH. Thanks to the camouflage of erythrocyte membrane (RM) and platelet membrane (PM), the nanosystem in question possesses remarkable features including immune escape and self-targeting. Therefore, a compact nano-core with PLGA@P/R was formed, with a hybrid membrane covering the surface of the core, forming a "core-shell" structure. With its "core-shell" structure, this nanoparticle fancifully combines the advantages of both PFH (the low-intensity focused ultrasound (LIFU)-responsive phase-change thrombolysis) and Rg1(the antioxidant, anti-inflammatory and anticoagulant abilities). Meanwhile, PM/RM@PLGA@P/R nanoparticles exhibits superior in-vitro performance in terms of ROS scavenging, anticoagulant activity and immune escape compared with those without cell membranes (PLGA@P/R). Furthermore, in the animal experiment in which the tail vein thrombosis model was established by injecting k-carrageenan, the combined treatment of LIFU and PM/RM@PLGA@P/R showed a satisfactory antithrombotic efficiency (88.20 %) and a relatively higher biological safety level. This strategy provides new insights into the development of more effective and safer targeted biomimetic nanomedicines for antithrombotic treatments, possessing potential application in synergistic therapy field.

Use of the RCOG risk assessment model and biomarkers to evaluate the risk of postpartum venous thromboembolism

BACKGROUND

Venous thromboembolism (VTE) is a leading cause of morbidity and mortality during pregnancy and the puerperium. The vast majority of VTE occurs after childbirth. China has not yet established standard risk assessment model for postpartum venous thromboembolism (VTE), the Royal College of Obstetricians and Gynecologists (RCOG) risk assessment model (RAM) is commonly used in clinic at present. Herein, we aimed to evaluate the validity of the RCOG RAM in the Chinese population and try to formulate a local risk assessment model by combining with other biomarkers for VTE prophylaxis.

METHODS

The retrospective study was conducted from January 2019 to December 2021at Shanghai First Maternity and Infant Hospital which has approximately 30,000 births annually, and the incidence of VTE, differences between RCOG-recommended risk factors, and other biological indicators from medical records were evaluated.

RESULTS

The study included VTE (n = 146) and non-VTE(n = 413) women who examined by imaging for suspicion of postpartum VTE. There was no statistical difference in the incidence rate of postpartum VTE between the low-score group (23.8%) and the high-score group (28%) after stratification by RCOG RAM. However, we found that cesarean section (in the low-score group), white blood cell (WBC) ≥ 8.64*10^9/L (in the high-score group), low-density lipoprotein(LDL) ≥ 2.70 mmol/L, and D-dimer ≥ 3.04 mg/L (in both groups) were highly associated with postpartum VTE. Subsequently, the validity of the RCOG RAM combined with biomarkers as a model for the risk assessment of VTE was estimated and the results showed that this model has good accuracy, sensitivity, and specificity.

CONCLUSIONS

Our study indicated that the RCOG RAM was not the best strategy for predicting postpartum VTE. Combined with some biomarkers (including the value of LDL and D-Dimer, and WBC count), the RCOG RAM is more efficient when identifying high-risk groups of postpartum VTE in the Chinese population.

TRIAL REGISTRATION

This purely observational study does not require registration based on ICMJE guidelines.

Multi-omic molecular profiling and network biology for precision anaesthesiology: a narrative review

Technological advancement, data democratisation, and decreasing costs have led to a revolution in molecular biology in which the entire set of DNA, RNA, proteins, and various other molecules - the 'multi-omic' profile - can be measured in humans. Sequencing 1 million bases of human DNA now costs US$0.01, and emerging technologies soon promise to reduce the cost of sequencing the whole genome to US$100. These trends have made it feasible to sample the multi-omic profile of millions of people, much of which is publicly available for medical research. Can anaesthesiologists use these data to improve patient care? This narrative review brings together a rapidly growing literature in multi-omic profiling across numerous fields that points to the future of precision anaesthesiology. Here, we discuss how DNA, RNA, proteins, and other molecules interact in molecular networks that can be used for preoperative risk stratification, intraoperative optimisation, and postoperative monitoring. This literature provides evidence for four fundamental insights: (1) Clinically similar patients have different molecular profiles and, as a consequence, different outcomes. (2) Vast, publicly available, and rapidly growing molecular datasets have been generated in chronic disease patients and can be repurposed to estimate perioperative risk. (3) Multi-omic networks are altered in the perioperative period and influence postoperative outcomes. (4) Multi-omic networks can serve as empirical, molecular measurements of a successful postoperative course. With this burgeoning universe of molecular data, the anaesthesiologist-of-the-future will tailor their clinical management to an individual's multi-omic profile to optimise postoperative outcomes and long-term health.

Pathophysiological, immunogenetic, anatomopathological profile of thrombophilia in pregnancy

Thrombophilic states have been associated with early and/or late pregnancy loss and possibly other severe obstetrical complications. Pregnancy-induced hypercoagulability, increased stasis, and the consequences of inherited and acquired thrombophilia are just a few of the factors that contribute to the development of thrombosis in pregnancy. In this review, we illustrate the impact that these factors have on the development of thrombophilia during pregnancy. We also explore how thrombophilia impact pregnancy outcomes. Next, we discuss how human leukocyte antigen G plays a part in thrombophilia during pregnancy by regulating cytokine release to prevent trophoblastic cell invasion and maintain local immunotolerance constant. Human leukocyte antigen class E is briefly explored with thrombophilia in pregnancy. Regarding the anatomopathologic aspect, we describe the different histopathological lesions of the placenta found in women with thrombophilia.

Prevalence of Inherited Thrombophilia in Women with Recurrent Pregnancy Loss During the First Trimester of Pregnancy

Purpose

This study aims to investigate the prevalence of inherited thrombophilia in women with recurrent pregnancy loss during the first trimester of pregnancy. The study was assessed the potential role of inherited thrombophilia in recurrent miscarriages and evaluate the consequences of this condition on the reproductive outcomes of affected women.

Material and Methods

This study was an analytical descriptive carried out in Khartoum, Sudan. The research comprised 98 controls who had given birth twice or more without experiencing a miscarriage and 120 patients. Each patient had done more than two miscarriages especially when the pregnancy is at its beginning trimester. (APCR), and (PS) were investigated using the clotting approach. There was an assessment of biological activities of (ATIII), (PC), and (PS) for both groups using the chromogenic method.

Results

The average age of the patients was 34, which was higher than the average age of the controls (33.5). The patient group had a much higher rate of multiple miscarriages among the women.: 35 (29.17%), 45 (37.50%), and 40 (33.33%). The incidence of PC deficiencies was determined to be 1.02% (1/98), whereas neither ATIII nor PS deficiencies were seen in the control group (0/98). APCR was more prevalent in the control group (4.10% or 4/98).

Conclusion

Despite contradicting evidence to the contrary in the literature, our findings imply that most miscarriages occur when pregnancy is at the first trimester when a woman is pregnant and they are all caused by thrombophilia.

A Retrospective Assessment of Thrombophilia in Pregnant Women with First and Second Trimester Pregnancy Loss

Recurrent Pregnancy Loss (RPL) affects between 1% to 5% of women of reproductive age. It is widely believed that RPL is a complex disorder that is influenced by chromosomal abnormalities, genetic mutations, uterine anatomic deformity, endocrine dysfunction, immunologic factors, infections, and the environment. Thrombotic disorders are a frequent cause of RPL, accounting for almost half of all cases; however, in the rest of the cases, the cause of RPL remains unclear. Therefore, in this study, it was planned to determine the genetic mutations involved in RPL during the first and second trimester of pregnancy. An observational retrospective cohort study was conducted in 2021, collecting data from 157 first trimester miscarriages and 54 s trimester pregnancies. All patients with a panel of laboratory and genetic analysis for thrombophilia were included for data analysis. It was observed that four factors were significantly more prevalent in one of the groups. Factor V Leiden (FVL) homozygosity and antiphospholipid syndrome (APS) antibodies were statistically significantly more common in pregnant women who suffered first trimester pregnancy losses. On the other hand, Protein C deficiency and Glycoprotein Ia polymorphism were statistically significantly more frequent in the second trimester group. The strongest independent risk factors for first trimester pregnancy loss were FVL and prothrombin (PT) compound mutations (OR = 3.11), followed by FVL homozygous mutation (OR = 3.66), and APS antibodies (OR = 4.47). Regarding second trimester pregnancy loss risk factors, the strongest were FVL and PT compound (OR = 3.24), followed by Glycoprotein Ia polymorphism (OR = 3.61), and respectively, APS antibodies (OR = 3.85). Numerous thrombophilic risk factors for early and late pregnancy loss have been found, including several mutations that seem to occur more often either during the first or the second trimester. Even though we are aware of risk-free and efficient diagnostics for thrombophilia abnormalities, no intervention has been proved to be clearly successful after the detection of these variables.

Venous Thromboembolism During Pregnancy and the Postpartum Period: Risk Factors, Diagnostic Testing, and Treatment

Importance

The risk of venous thromboembolism (VTE) increases during pregnancy and the postpartum period. Deep vein thrombosis is the most common VTE during pregnancy, but pulmonary embolism is typically of greater concern as it contributes to far higher morbidity and mortality. Diagnosis and treatment of VTE during pregnancy differ substantially from the general nonpregnant population.

Objective

This review describes the epidemiology, risk factors, clinical presentation, diagnosis, and treatment of VTE during pregnancy and the postpartum period.

Evidence Acquisition

First, we reviewed the VTE guidelines from professional societies in obstetrics, cardiology, hematology, emergency medicine, pulmonology, and critical care. Second, we examined references from these documents and used PubMed to identify recent articles that cited the guidelines. Finally, we searched PubMed and Google Scholar for articles published since 2018 that included terms for pregnancy and the epidemiology, risk factors, diagnostic imaging, or treatment of VTE.

Results

Venous thromboembolism risk increases throughout pregnancy and peaks shortly after delivery. More than half of pregnancy-related VTE are associated with thrombophilia; other major risks include cesarean delivery, postpartum infection, and the combination of obesity with immobilization. Most VTE can be treated with low molecular weight heparin, but cases of limb- or life-threatening VTE require consideration of thrombolysis and other reperfusion therapies.

Conclusions and Relevance

Venous thromboembolism is far more frequent in antepartum and postpartum women than age-matched controls, and clinical suspicion for VTE in this population should incorporate pregnancy-specific risks. Treatment of limb- or life-threatening antepartum or postpartum VTE requires multispecialty coordination to optimize maternal and fetal outcomes.

Cerebral venous sinus thrombosis in pregnancy and puerperium

Cerebral venous sinus thrombosis (CVST) is more common in women than in men, possibly due to gender-specific risk factors in young adults. The purpose of this study was to investigate whether the clinical and radiological findings, other risk factors, and clinical course of CVST associated with pregnancy and puerperium differ from those of other CVST cases. We retrospectively reviewed patients diagnosed with CVST in our hospital between September 2007 and December 2019. The risk factors, clinical and radiological characteristics, and follow-up data for female patients with CVST were compared between cases associated with pregnancy and puerperium with those of other cases. A total of 50 female patients with CVST were included in the study. Twenty-four (48%) cases occurred during pregnancy and puerperium. The mean age of the pregnant or puerperal patients was lower than that of the other patients (p = 0.007). There was no significant difference between the groups in terms of clinical and neuroradiological findings or presence of any additional risk factors including hereditary thrombophilia. There was also no difference in terms of in-hospital mortality rates and modified Rankin Scale (mRS) scores at 6 months between the groups. The clinical presentation of CVST and the frequencies of the presence of other risk factors including genetic thrombophilia in pregnant and puerperal patients were similar to those of non-pregnant female patients. Screening for additional risk factors, especially genetic thrombophilia, should therefore not be neglected in CVST occurring during pregnancy and puerperium.

Inherited thrombophilia is significantly associated with severe preeclampsia

Methods to prevent the development of pathologies due to placental dysfunctions, such as gestational hypertension and preeclampsia, are the main approaches for obtaining the best maternal and fetal antepartum and postpartum prognosis. During 5 years of study (January, 2015 to December, 2019), the cases of pregnancy and puerperium complicated with pathology due to placental dysfunction were analyzed. The main objective was to determine the magnitude of the impact of thrombophilia on the development of an entity of gestational hypertension disorder. We compared the impact of thrombophilia and its associated complications in patients with gestational hypertension with moderate and severe preeclampsia. Thus, we found obesity, thrombophilia, and underlying cardiac pathology to be significant risk factors for severe preeclampsia. Regarding the comparative analysis of the risk factors and complications associated with patients with mild preeclampsia compared with those with severe preeclampsia, the presence in severe preeclampsia of thrombophilia, endocrine, liver, and cardiac pathology was higher and, a higher rate of complications was observed; complications included fetal death, intrauterine growth restriction (IUGR), prematurity, fetal arrhythmia with acute fetal distress, HELLP syndrome, and placental abruption. Thrombophilia has a significant effect on the development of severe preeclampsia, and oligohydramnios as specific complication of mild preeclampsia. Factors indicating an increased risk of progression from mild preeclampsia to severe preeclampsia are in addition to inherited thrombophilia the underlying pathologies, namely cardiac, hepatic, and endocrine factors.

Three-factorial Genetic Thrombophilia with Recurrent Thrombotic Events in a Saudi Patient: A Case Report

Thrombophilia is caused by several genetic and acquired factors. Existence of more than one genetic factor may increase the risk of developing recurrent thrombotic events. Here, we present a case of a 48-year-old male with a known history of deep venous thrombosis and a known mutation in factor V Leiden combined with mild protein S deficiency, who presented with a painful swelling in the left leg. Moreover, the patient had a history of diabetes, dyslipidemia and obesity. Prothrombin time and platelet count were within the normal range. The international normalized ratio and activated partial thromboplastin time were 3.21 and 36.7 s, respectively. The Doppler study showed a thrombus in the saphenous vein, and complementary genetic screening investigations revealed heterozygous mutation for prothrombin (G20210A). A diagnosis of multifactorial genetic thrombophilia was established. The patient was treated with warfarin, which resulted in significant improvement in the follow-ups, and at the time of reporting this case, there were no clinical or biological signs of thrombosis. The presence of multiple hereditary and acquired thrombophilic factors is a rare clinical presentation that requires close monitoring, for which a lifelong anticoagulation therapy should be discussed based on the clinical response of the patient.

Recurrent miscarriage is not associated with a higher prevalence of inherited and acquired thrombophilia

PROBLEM

Although not being recommended in guidelines, many physicians perform routine screening for thrombophilia in RM patients suspecting a higher prevalence in these patients. The aim of this study was to analyze the prevalence of inherited and acquired thrombophilia in a large cohort of RM patients.

METHOD OF STUDY

Within a multicenter case-control study, n = 820 RM patients and n = 141 controls were included. The prevalence of inherited and acquired thrombophilia including deficiency of protein C/S and antithrombin, elevation of factor VIII activity, APC resistance including mutation in the factor V Leiden gene, mutation in the prothrombin gene and antiphospholipid antibodies were assessed. Further, we performed a meta-analysis of the prevalence of thrombophilia in RM patients including studies between 01/2000 and 01/2020.

RESULTS

An antiphospholipid syndrome (APLS) was only present in RM patients. Increased factor VIII concentration was significantly more prevalent in controls (RM vs controls: 5.8% vs 11.0%). None of the other thrombophilia did differ significantly between RM patients and controls. The meta-analysis revealed no significant difference in the occurrence of these thrombophilia between RM patients and controls.

CONCLUSION

The prevalence of inherited thrombophilia does not differ between RM patients and controls. When analyzing rare events like thrombophilia, a high number of patients are needed to obtain reliable results, which might explain contradictory findings in previous studies analyzing small cohorts of RM patients. Despite being less prevalent than previously described, we still recommend screening for APLS as it is associated with severe pregnancy complications.

Genetic mutations associated with susceptibility to perioperative complications in a longitudinal biorepository with integrated genomic and electronic health records

BACKGROUND

Existing genetic information can be leveraged to identify patients with susceptibilities to conditions that might impact their perioperative care, but clinicians generally have limited exposure and are not trained to contextualise this information. We identified patients with genetic susceptibilities to anaesthetic complications using a perioperative biorepository and characterised the concordance with existing diagnoses.

METHODS

Adult patients undergoing surgery within Michigan Medicine from 2012 to 2017 were consented for genotyping. Genotypes were integrated with the electronic health record (EHR). We retrospectively characterised frequencies of variants associated with butyrylcholinesterase deficiency, factor V Leiden, and malignant hyperthermia, three pharmacogenetic factors with perioperative implications. We calculated the percentage homozygous and heterozygous for each that had been diagnosed previously and searched for EHR findings consistent with a predisposition.

RESULTS

Analysis of genetic data revealed that 25 out of 40 769 (0.1%) patients were homozygous and 1918 (4.7%) were heterozygous for mutations associated with butyrylcholinesterase deficiency. Of the homozygous individuals, 14 (56%) carried a pre-existing diagnosis. For factor V Leiden, 29 (0.1%) were homozygous and 2153 (5.3%) heterozygous. Of the homozygous individuals, three (10%) were diagnosed by EHR-derived phenotype and six (21%) by clinician review. Malignant hyperthermia was assessed in a subset of patients. We detected two patients with associated mutations. Neither carried clinical diagnoses.

CONCLUSIONS

We identified patients with genetic susceptibility to perioperative complications using an open source script designed for clinician use. We validated this application in a retrospective analysis for three conditions with well-characterised inheritance, and showed that not all genetic susceptibilities were documented in the EHR.

Prophylaxis and Therapy of Venous Thrombotic Events (VTE) in Pregnancy and the Postpartum Period

Venous thromboembolisms and pulmonary embolisms are one of the main causes of morbidity and mortality in pregnancy. The increased risk of thrombotic events caused by the physiological changes during pregnancy alone does not justify any medical antithrombotic prophylaxis. However, if there are also other risk factors such as a history of thromboses, hormonal stimulation as part of fertility treatment, thrombophilia, increased age of the pregnant woman, severe obesity or predisposing concomitant illnesses, the risk of thrombosis should be re-evaluated - if possible by a coagulation specialist - and drug prophylaxis should be initiated, where applicable. Low-molecular-weight heparins (LMWH) are the standard medication for the prophylaxis and treatment of thrombotic events in pregnancy and the postpartum period. Medical thrombosis prophylaxis started during pregnancy is generally continued for about six weeks following delivery due to the risk of thrombosis which peaks during the postpartum period. The same applies to therapeutic anticoagulation after the occurrence of a thrombotic event in pregnancy; here, a minimum duration of the therapy of three months should also be adhered to. During breastfeeding, LMWH or the oral anticoagulant warfarin can be considered; neither active substance passes into breast milk.

Identifying cross-disease components of genetic risk across hospital data in the UK Biobank

Genetic risk factors frequently affect multiple common human diseases, providing insight into shared pathophysiological pathways and opportunities for therapeutic development. However, systematic identification of genetic profiles of disease risk is limited by the availability of both comprehensive clinical data on population-scale cohorts and the lack of suitable statistical methodology that can handle the scale of and differential power inherent in multi-phenotype data. Here, we develop a disease-agnostic approach to cluster genetic risk profiles for 3,025 genome-wide independent loci across 19,155 disease classification codes from 320,644 participants in the UK Biobank, representing a large and heterogeneous population. We identify 339 distinct disease association profiles and use multiple approaches to link clusters to underlying biological pathways. We show how clusters can decompose the variance and covariance in risk for disease, thereby identifying underlying biological processes and their impact. We demonstrate the use of clusters in defining disease relationships and their potential in informing therapeutic strategies.

Pregnancy-related thrombosis risk in patients with protein C deficiency and comparison with pregnant women with heterozygous factor V Leiden mutation

: The risk of pregnancy-related venous thromboembolism is high in patients with inherited thrombophilia. The aim of this study was to compare the risk of pregnancy related-venous thromboembolism of women with protein C (PC) deficiency to patients with heterozygous factor V Leiden mutation. 145 consecutive pregnant women with confirmed PC deficiency or heterozygous factor V Leiden mutation were prospectively enrolled in the study. Lyon venous thromboembolism-risk score was used to individually tailor antithrombotic prophylaxis. The use of a validated clinical score presents the advantage to have a homogenous management of the venous thromboembolism risk in patients having similar risk factors. 53 pregnancies with PC deficiency were compared with 190 pregnancies in heterozygous factor V Leiden mutation carriers. 50% of the patients with PC deficiency and 64% of the heterozygous factor V Leiden mutation carriers were asymptomatic. According to the Lyon-venous thromboembolism risk score, 50% of patients with PC deficiency and 51% of heterozygous factor V Leiden carriers did not received any antepartum heparin prophylaxis. 34 and 37% of patients respectively received heparin prophylaxis during the third trimester only. No venous thromboembolism was observed in patients with PC deficiency and one postpartum venous thromboembolism occurred in a patient with heterozygous factor V Leiden. In the absence of randomized controlled clinical studies, we report here a large prospective series of pregnant women with PC deficiency. In our cohort, no difference of outcome, in terms of venous thromboembolism, was observed between pregnant women with PC deficiency and those with heterozygous factor V Leiden. Based on our results, low-molecular-weight heparin prophylaxis should not be mandatory in all pregnant women with PC deficiency. Similar prophylaxis strategies may be applied to women with factor V Leiden mutation or PC deficiency.

ACOG Practice Bulletin No. 197: Inherited Thrombophilias in Pregnancy

Inherited thrombophilias are associated with an increased risk of venous thromboembolism and have been linked to adverse outcomes in pregnancy. However, there is limited evidence to guide screening for and management of these conditions in pregnancy. The purpose of this document is to review common thrombophilias and their association with maternal venous thromboembolism risk and adverse pregnancy outcomes, indications for screening to detect these conditions, and management options in pregnancy. This Practice Bulletin has been revised to provide additional information on recommendations for candidates for thrombophilia evaluation, updated consensus guidelines regarding the need for prophylaxis in women with an inherited thrombophilia during pregnancy and the postpartum period, and discussion of new published consensus guidelines from the Society for Obstetric Anesthesia and Perinatology addressing thromboprophylaxis and neuraxial anesthetic considerations in the obstetric population.

Clinical and laboratory manifestations of the prothrombin gene mutation in women of reproductive age

Research objective

To research the association of prothrombin (factor II) activity given the prothrombin G20210A mutation carriage with its clinical manifestations as thrombotic complications.

Materials and methods

A prospective clinical cohort study of 290 women of reproductive age was conducted. Two cohort groups were identified: the study group of 140 patients with prothrombin mutation G20210A genotype and the control group of 150 women with G20210G genotype.

Results

The prothrombin G20210A mutation carriage is associated with the risk of thrombotic complications compared to the wild G20210G type (RR =17.1; p<0.0001) and is characterized by thrombosis localized both in the venous (66.7%) and arterial (33.3%) vascular pools. The threshold value of prothrombin activity (174.8%) for G20210A genotype was calculated, making it possible to conclusively predict the risk of thrombotic events with the accuracy of 90.4%.

Conclusion

The phenotypic manifestation of the prothrombin G20210A mutation in the form of venous and arterial thromboses in women of reproductive age is associated with a super-threshold increase in prothrombin (factor II) activity, which makes it possible to stratify the patients into the group of high risk of thromboses.

Pearls in clinical obstetrics: challenges in anticoagulation in pregnancy

Women are at increased risk for venous thromboembolism (VTE) during both pregnancy and in the post-partum period. We have conducted a comprehensive literature review of the use of anticoagulation in pregnancy for pregnant women at increased risk for VTE. Multiple factors, including physiologic and pharmacokinetic changes make the treatment and prevention of VTE complicated in pregnancy. Adequate treatment and prevention of VTE in pregnancy is critically important, yet good quality medical studies continue to be lacking. There is a growing amount of data for the use of low molecular weight heparin (LMWH) in pregnant women and this remains the treatment of choice in most indications. For both prophylactic and therapeutic treatments, when LMWHs are chosen, monitoring of antifactor Xa level, although controversial, is advised. Women with prosthetic valve who become pregnant face challenges in regard of type of anticoagulation, dosing and monitoring during pregnancy. Delivery options and peripartum care should be defined with a multidisciplinary approach and taking patient's preference and autonomy in consideration. More high-quality research on this topic is needed to guide the clinical care of this unique population.

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

Background

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

Case presentation

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

Conclusions

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

High prevalence of factor V Leiden and prothrombin G20101A mutations in Kashmiri patients with venous thromboembolism

AIM

The genetic variants of the factor V (G1691A), prothrombin (G20210A) and MTHFR (C677T) genes have been widely implicated as inherited risk factors for developing venous thrombosis. This study was undertaken to reveal the frequency of these mutations in Kashmiri patients with venous thromboembolism.

METHODOLOGY

A case-control study was designed with 250 VTE patients and 250 healthy controls. The mutations were analysed using ARMS-PCR and PCR-RFLP approach.

RESULT

The factor V Leiden G1691A mutation was found in 17/250 (6.8%) VTE patients and prothrombin G20210A mutation was found in 7/250 (2.8%) VTE patients while no mutation was found in any of the healthy controls. Both the mutations were found to be significantly associated with the increased risk of VTE (p = 0.0001 and 0.0150 respectively) while no association of VTE risk with MTHFR C677T polymorphism was found (p = 0.53).

CONCLUSION

The increased frequency of factor V Leiden G1691A and prothrombin G20210A mutation in VTE patients indicates a significant role of these mutations in the development of VTE in our population. We therefore suggest the routine screening of these two mutations as thrombophilic markers in Kashmiri patients with venous thromboembolism.

Differential haemostatic risk factors for pregnancy-related deep-vein thrombosis and pulmonary embolism

Limited data exist on thrombophilia and the risk of venous thrombosis (VT) during pregnancy and postpartum. The objectives of the present study were to investigate the role of haemostatic risk factors for pregnancy-related VT and their phenotypic expression in deep-vein thrombosis (DVT) and pulmonary embolism (PE). Total 313 cases with objectively verified first time VT and 353 controls were selected from a source population of 377,155 women with 613,232 pregnancies. The adjusted odds ratio (aOR) for pregnancy-related VT was 1.7 (95% confidence interval [CI] 1.1–2.8) for women with factor VIII >90th percentile. The aOR for VT for endogenous thrombin potential and D-dimer values >90thpercentiles were 1.8 (95% CI 1.1–3.0) and 2.1 (95% CI 1.3–3.3), respectively. Factor IX >90thpercentile or free protein S ≤the 5th percentile increased the risk for PE, and the aORs were 2.4 (95% CI 1.1–5.0) and 3.1 (95% CI 1.3–7.2), respectively. Women carrying the factor V Leiden (F5 rs6025) polymorphism, or who had reduced sensitivity to activated protein C (aPC) in the absence of F5 rs6025, had increased risk for DVT, with unadjusted ORs 7.7 (95% CI 4.7–12.7) and 3.5 (95% CI 2.2–5.4), respectively. Women with a history of pregnancy-related VT showed activation of coagulation and had elevated factor VIII. Furthermore, high levels of factor IX and low levels of free protein S were associated with increased risk for PE, whereas aPC resistance and F5 rs6025 were risk factors for DVT and not PE.

Population-based Study of Risk Polymorphisms Associated with Vascular Disorders and Dementia

Introduction:

Cardiovascular and neurodegenerative disorders are among the major causes of mortality in the developed countries. Population studies evaluate the genetic risk, i.e. the probability of an individual carrying a specific disease-associated polymorphism. Identification of risk polymorphisms is essential for an accurate diagnosis or prognosis of a number of pathologies.

Aims:

The aim of this study was to characterize the influence of risk polymorphisms associated with lipid metabolism, hypertension, thrombosis, and dementia, in a large population of Spanish individuals affected by a variety of brain and vascular disorders as well as metabolic syndrome.

Material & Method:

We performed a cross-sectional study on 4415 individuals from a widespread regional distribution in Spain (48.15% males and 51.85% females), with mental, neurodegenerative, cerebrovascular, and metabolic disorders. We evaluated polymorphisms in 20 genes involved in obesity, vascular and cardiovascular risk, and dementia in our population and compared it with representative Spanish and European populations. Risk polymorphisms in ACE, AGT(235), IL6(573), PSEN1, and APOE (specially the APOE-ε4 allele) are representative of our population as compared to the reference data of Spanish and European individuals.

Conclusion:

The significantly higher distribution of risk polymorphisms in PSEN1 and APOE-ε4 is characteristic of a representative number of patients with Alzheimer’s disease; whereas polymorphisms in ACE, AGT(235), and IL6(573), are most probably related with the high number of patients with metabolic syndrome or cerebrovascular damage.

Genetic Risk Factors in Cerebrovascular Disorders and Cognitive Deterioration

INTRODUCTION

The study of variations in genes involved in the different events that trigger the atherogenic process, such as lipid metabolism (modification of LDL-cholesterol), endothelial function and hypertension, immune response (recruitment of macrophages and foam cell formation) and stability of atherosclerotic plaques (thrombosis), established the risk for suffering a vascular disorder. A total of 2455 cases over 50 years of age were genotyped for a panel of 19 SNPs in 15 genes encoding for proteins involved in the atherogenic process. This study shows the relevance of polymorphisms in APOB (odds ratio (OR), 1.17; 95% confidence interval (95% CI), 0.74-1.85), APOC3 (OR, 1.33; 95% CI, 0.82-2.17) and APOE (OR, 1.75; 95% CI, 1.09-2.80), as genetic risk markers for hypercholesterolemia; polymorphisms in ACE (OR, 1.68; 95% CI, 0.32-8.77) and AGT (OR, 1.74; 95% CI, 0.97-3.14) for hypertension; and in APOE*3/*4 (OR, 2.06; 95% CI, 1.70-2.51) and APOE*4/*4 (OR, 3.08; 95% CI, 1.85-5.12) as unambiguous markers of dementia.

RESULT

Our results also showed the transversal importance of proinflammatory cytokines in different stages of atherogenesis, with special relevance of IL6 (OR, 1.39; 95% CI, 0.56-3.49) and TNF (OR, 1.40; 95% CI, 0.92-2.15) related to hypercholesterolemia and hypertension. The set of markers involved in this genetic risk panel makes it a powerful tool in the management of patients with different vascular disorders.

Double versus single thrombophilias during pregnancy

OBJECTIVE

The primary objective of this study was to evaluate whether women with double thrombophilias have a greater risk for obstetric complications as compared with women who have single thrombophilias.

STUDY DESIGN

This is a retrospective cohort study of all patients in a single practice with a clinically significant inherited thrombophilia and treated with anticoagulation between 2005 and 2013. Thrombophilias evaluated include: factor V Leiden, prothrombin G20210A gene mutation, protein S deficiency, protein C deficiency, and antithrombin III deficiency. Double thrombophilia was defined as the presence of two thrombophilias or homozygosity for factor V Leiden or prothrombin Gene Mutation. Demographic and obstetrical outcome data were collected. Data on all patients with double thrombophilias who met inclusion criteria was reported. Data was then compared between the patients with double thrombophilias and single thrombophilias with singleton gestations. The data was analyzed with Pearson's chi-squared or Student's t-test as appropriate with p value <.05 used for significance.

RESULTS

Eighteen patients with clinically significant double thrombophilias who met inclusion criteria were identified. Most patients delivered full term (88.9%) and appropriate for gestational age (77.8%) infants. One hundred thirty-two patients with single thrombophilias and 14 patients with double thrombophilias with singleton gestations were then compared. Demographic characteristics were not significantly different between the two groups. There were no significant differences in obstetrical outcomes between patients.

CONCLUSIONS

There were no significant differences in obstetrical outcomes for patients with clinically significant double thrombophilias versus single thrombophilias when treated with anticoagulation.

Management of Venous Thromboembolism in Patients with Hereditary Antithrombin Deficiency and Pregnancy: Case Report and Review of the Literature

Background. Hereditary antithrombin deficiency is a thrombogenic disorder associated with a 50–90% lifetime risk of venous thromboembolism (VTE), which is increased during pregnancy and the puerperium in these patients. We present a case of a woman with antithrombin (AT) deficiency who presented with a VTE despite therapeutic low molecular weight heparin (LMWH). Though the pregnancy was deemed unviable, further maternal complications were mitigated through the combined use of therapeutic anticoagulation and plasma-derived antithrombin concentrate infusions to normalize her functional antithrombin levels. Methods. A review of the literature was conducted for studies on prophylaxis and management of VTE in pregnant patients with hereditary AT deficiency. The search involved a number of electronic databases, using combinations of keywords as described in the text. Only English language studies between 1946 and 2015 were included. Conclusion. Antithrombin concentrate is indicated in pregnant women with hereditary AT deficiency who develop VTE despite being on therapeutic dose anticoagulation. Expert opinion suggests AT concentrate should be used concomitantly with therapeutic dose anticoagulation. However, further high-quality studies on the dose and duration of treatment in the postpartum period are required. Use of AT concentrate for prophylaxis is controversial and should be based on individual VTE risk stratification.

Venous Thromboembolism in Pregnancy

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

Hereditary risk factors for thrombophilia and probability of venous thromboembolism during pregnancy and the puerperium

Venous thromboembolism (VTE) is a leading cause of maternal mortality. Few studies have evaluated the individual risk of gestational VTE associated with heritable thrombophilia, and current recommendations for antenatal thromboprophylaxis in women with severe thrombophilia such as homozygous factor V Leiden mutation (FVL) depend on a positive family history of VTE. To better stratify thromboprophylaxis in pregnancy, we aimed to estimate the individual probability (absolute risk) of gestational VTE associated with thrombophilia and to see whether these risk factors are independent of a family history of VTE in first-degree relatives. We studied 243 women with the first VTE during pregnancy and the puerperium and 243 age-matched normal women. Baseline incidence of VTE of 1:483 pregnancies in women ≥35 years and 1:741 deliveries in women <35 years was assumed, according to a recent population-based study. In women ≥35 years (<35 years), the individual probability of gestational VTE was as follows: 0.7% (0.5%) for heterozygous FVL; 3.4% (2.2%) for homozygous FVL; 0.6% (0.4%) for heterozygous prothrombin G20210A; 8.2% (5.5%) for compound heterozygotes for FVL and prothrombin G20210A; 9.0% (6.1%) for antithrombin deficiency; 1.1% (0.7%) for protein C deficiency; and 1.0% (0.7%) for protein S deficiency. These results were independent of a positive family history of VTE. We provide evidence that unselected women with these thrombophilias have an increased risk of gestational VTE independent of a positive family history of VTE. In contrast to current guidelines, these data suggest that women with high-risk thrombophilia should be considered for antenatal thromboprophylaxis regardless of family history of VTE.

Molecular Analysis of Factor V Leiden, Factor V Hong Kong, Factor II G20210A, Methylenetetrahydrofolate Reductase C677T, and A1298C Mutations Related to Turkish Thrombosis Patients

Inherited gene disorders related to the hemostatic system have been documented as risk factors for thrombosis. The roles of factor V Hong Kong (FV Hong Kong), factor V Leiden (FV Leiden), factor II G20210A (FII G20210A), methylenetetrahydrofolate reductase (MTHFR) C677T, and MTHFR A1298C mutations in Turkish patients with thrombosis (270 patients) compared with healthy controls (114 subjects) were evaluated. Polymerase chain reaction—based restriction enzyme analysis was carried out to screen these mutations, and single-strand conformation analysis was established to identify variations using the primers selected for restriction enzyme analysis studies. As a result, a significant relationship was determined among FV Leiden, FII G20210A, and thrombosis. The FV Hong Kong mutation was observed in only 2 patients with pulmonary vein thrombosis who are FV Leiden/FV Hong Kong compound heterozygous for FV gene. MTHFR C677T and A1298C were equally distributed in the patient group compared with the control group. All named mutations were also identified with single-strand conformation analysis, but a new variant/polymorphism during studies was not found. Because some inherited abnormalities are associated with thromboembolic disorders, determining the mutations and gene-to-gene interactions in patients with thrombosis history has a great impact on diagnosis and treatment of these diseases.

Genetic Risk Factors in Venous Thromboembolism

Genetic risk factors predispose to thrombophilia and play the most important etiopathogenic role in venous thromboembolism (VTE) in people younger than 50 years old. At least one inherited risk factor could be found in about half of the cases with a first episode of idiopathic VTE.Roughly, genetic risk factors are classified into two main categories: loss of function mutations (such as deficiencies of antithrombin, protein C, protein S) and gain of function mutations, (such as prothrombin mutation G20210A, factor V Leiden). A revolutionary contribution to the genetic background of VTE was brought by the achievements of the genome-wide association studies which analyze the association of a huge number of polymorphisms in large sample size.Hereditary thrombophilia testing should be done only in selected cases. The detection of hereditary thrombophilia has impact on the management of the anticoagulation in children with purpura fulminans, pregnant women at risk of VTE and may be useful in the assessment of the risk for recurrent thrombosis in patients presenting an episode of VTE at a young age (<40 years) and in cases with positive family history regarding thrombosis.

Factor V Leiden, Prothrombin and MTHFR Mutation in Patients with Preeclamsia, Intrauterine Growth Restriction and Placental Abruption

BACKGROUND

Factor V Leiden, Prothrombin and MTHFR gene mutation, could have an influence in pregnancy with adverse outcome Preeclamsia, IUGR and Placental abruption.

AIM

The aim of this study is to investigate the presence of above mentioned inherited thrombophilias and its statistical significance, distribution among the complicated and normal pregnancy, and relative risk for carrier of mutation to develop preeclampsia, IUGR and placental abruption.

MATERIAL AND METHODS

Prospective cohort study is implemented at University Clinic for Obstetric and Gynecology in Skopje, Republic of Macedonia. The study included 109 delivered patients: 40 with preeclapmsia, 22 with IUGR, 17 with placental abruption and 30 as control group with normal pregnancy. The amount of 3 ml venous blood has been used for detection of these point mutations using ThromboStrip -Opegen, QIAGEN kit manufactured for thrombotic risk.

RESULTS

The highest frequency was found: in the group with preeclampsia 35% were MTHFR homozygous, IUGR -MTHFR heterozygous 45%, Placental abruption- 52.9% MTHFR heterozygous, and in the control group without thrombophilia 56.7%. There were combined thrombophilia in 3 patients. There aren`t statistical significance in presence of thrombophilia among groups (p > 0.05). Statistical significance (p < 0.05) was found between carriers of MTHFR homozygous in preeclampsia and group with placental abruption and control group. Relative risk in IUGR group for MTHFR homozygous was 5.54 (1.37

CONCLUSION

The presence of mutation MTHFR homozygous could increase the risk for development of IUGR and mutation of Factor V Leiden for placental abruption. Further investigations with more patients are warranted.

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Key Words

• IUGR
• MTHFR
• factor V Leiden
• placental abruption
• preeclampsia
• prothrombin

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MESH Headings Collapse

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Affiliation(s) Collapse

Epidemiology of venous thromboembolism (VTE) associated with pregnancy

This review is focused on the epidemiology of venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), associated with pregnancy. Superficial vein thrombosis, a less hazardous and less studied type of thrombosis in pregnant women, is beyond the scope of this review. This study discusses the VTE incidence rate in women from developed countries for both antepartum and postpartum periods and for subpopulations of women affected by additional risk factors, such as thrombophilias, circulatory diseases, preeclampsia of varying degrees of severity, and Caesarean section. To minimize bias due to historical changes in medical and obstetric practices, lifestyle, diet, etc., this review is generally limited to relatively recent studies, i.e., those that cover the last 35 years. The absolute risk or incidence rate was used to ascertain risk of VTE associated with pregnancy. For the studies where the direct incidence rates of VTE were not reported, we calculated an estimate of the observed but not reported absolute incidence rates using the data presented in respective articles.

Thrombosis in pregnancy and maternal outcomes

Pregnancy increases the risk of thrombosis four- to five-fold. Seventy-five to eighty percent of pregnancy-related thrombotic events are venous and twenty to -twenty-five percent are arterial. The main reason for the increased risk is hypercoagulability. Women are hypercoagulable because they have evolved so that they are protected against the bleeding challenges of pregnancy, miscarriage, or childbirth. Both genetic and acquired risk factors can further increase the risk of thrombosis. The maternal consequences of thrombosis of pregnancy include permanent vascular damage, disability, and death. While the maternal outcomes of thrombosis can be modified by anticoagulation therapy, management of thrombosis during pregnancy is the subject of another paper in this issue (see paper by B. Konkle). This review will focus on the epidemiology, pathophysiology, risk factors, and maternal consequences of thrombosis in pregnancy.

Thrombophilia and venous thromboembolism in pregnancy: a meta-analysis of genetic risk

Three common polymorphic variants, namely Factor V Leiden (FVL), Prothrombin G20210A (PT G20210A) and Methylenetetrahydrofolate Reductase (MTHFR) C677T are candidate genes for venous thromboembolism (VTE) in pregnancy. We performed a literature review and meta-analysis of pertinent genetic association studies (GAS) in pregnancy, to quantify the genetic risk of VTE in pregnancy. We used the model-free approach of generalized odds ratio (ORG) to estimate gene-to-disease association and explored the mode of inheritance using the degree of dominance h index. Twelve case-control GAS studies provided the full genotype distributions for at least one candidate gene to assess the genetic risk. FVL was associated with a significant risk of VTE in pregnancy (ORG 7.28; 95% confidence interval 5.53-9.58) and a dominant mode of inheritance (h=0.76), that is the effect of heterozygous carriers will lie close to the homozygous mutant genotype. PT G20210A mutation was also associated with a significant VTE risk (ORG 5.43; 95% CI 3.66-8.03) and had an over-dominant mode of inheritance (h=1.5), suggesting that the effect of heterozygous carriers may exceed that of homozygous mutant. MTHFR C677T had no association with VTE risk in pregnancy (ORG 1.24; 95% CI 0.88-1.73). Our analysis provided robust data on VTE in pregnancy, relative to FVL and PT G20210A status and suggested that the genetic effects of heterozygous over homozygous carriers do not justify stratification of heterozygous as "lower risk" over homozygous mutants. On clinical grounds this may impact decisions to preferentially exclude heterozygous from anticoagulation prophylaxis.

Antepartum dalteparin versus no antepartum dalteparin for the prevention of pregnancy complications in pregnant women with thrombophilia (TIPPS): a multinational open-label randomised trial

BACKGROUND

Thrombophilias are common disorders that increase the risk of pregnancy-associated venous thromboembolism and pregnancy loss and can also increase the risk of placenta-mediated pregnancy complications (severe pre-eclampsia, small-for-gestational-age infants, and placental abruption). We postulated that antepartum dalteparin would reduce these complications in pregnant women with thrombophilia.

METHODS

In this open-label randomised trial undertaken in 36 tertiary care centres in five countries, we enrolled consenting pregnant women with thrombophilia at increased risk of venous thromboembolism or with previous placenta-mediated pregnancy complications. Eligible participants were randomly allocated in a 1:1 ratio to either antepartum prophylactic dose dalteparin (5000 international units once daily up to 20 weeks' gestation, and twice daily thereafter until at least 37 weeks' gestation) or to no antepartum dalteparin (control group). Randomisation was done by a web-based randomisation system, and was stratified by country and gestational age at randomisation day with a permuted block design (block sizes 4 and 8). At randomisation, site pharmacists (or delegates) received a randomisation number and treatment allocation (by fax and/or e-mail) from the central web randomisation system and then dispensed study drug to the local coordinator. Patients and study personnel were not masked to treatment assignment, but the outcome adjudicators were masked. The primary composite outcome was independently adjudicated severe or early-onset pre-eclampsia, small-for-gestational-age infant (birthweight <10th percentile), pregnancy loss, or venous thromboembolism. We did intention-to-treat and on-treatment analyses. This trial is registered with ClinicalTrials.gov, number NCT00967382, and with Current Controlled Trials, number ISRCTN87441504.

FINDINGS

Between Feb 28, 2000, and Sept 14, 2012, 292 women consented to participate and were randomly assigned to the two groups. Three women were excluded after randomisation because of ineligibility (two in the antepartum dalteparin group and one in the control group), leaving 146 women assigned to antepartum dalteparin and 143 assigned to no antepartum dalteparin. Some patients crossed over to the other group during treatment, and therefore for on-treatment and safety analysis there were 143 patients in the dalteparin group and 141 in the no dalteparin group. Dalteparin did not reduce the incidence of the primary composite outcome in both intention-to-treat analysis (dalteparin 25/146 [17·1%; 95% CI 11·4-24·2%] vs no dalteparin 27/143 [18·9%; 95% CI 12·8-26·3%]; risk difference -1·8% [95% CI -10·6% to 7·1%)) and on-treatment analysis (dalteparin 28/143 [19·6%] vs no dalteparin 24/141 [17·0%]; risk difference +2·6% [95% CI -6·4 to 11·6%]). In safety analysis, the occurrence of major bleeding did not differ between the two groups. However, minor bleeding was more common in the dalteparin group (28/143 [19·6%]) than in the no dalteparin group (13/141 [9·2%]; risk difference 10·4%, 95% CI 2·3-18·4; p=0·01).

INTERPRETATION

Antepartum prophylactic dalteparin does not reduce the occurrence of venous thromboembolism, pregnancy loss, or placenta-mediated pregnancy complications in pregnant women with thrombophilia at high risk of these complications and is associated with an increased risk of minor bleeding.

FUNDING

Canadian Institutes of Health Research, Heart and Stroke Foundation of Canada, and Pharmacia and UpJohn.