Prophylaxis with low-dose low-molecular-weight heparin during pregnancy and postpartum: is it effective?

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.

High rates of venous thromboembolism among deliveries complicated by cancer

BACKGROUND

Venous thromboembolism (VTE) risk is increased independently by both cancer and pregnancy.

OBJECTIVES

To estimate VTE risk in the postpartum period among patients delivering with a cancer diagnosis, stratified by cancer type and delivery route.

METHODS

We performed a retrospective cohort study utilizing the large, all-payer Nationwide Readmissions Database from October 2015 through December 2020. We identified delivery hospitalizations, cancer diagnoses, and VTE using patient demographics and diagnosis codes. The primary outcome was VTE incidence at 42 and 330 days from delivery admission date, comparing patients with and without cancer diagnoses. A secondary analysis included VTE risk stratified by cancer diagnosis and delivery route. Outcomes were compared using inverse probability-weighted survival curves.

RESULTS

The study population included 9 793 503 delivery hospitalizations (weighted estimate, 18 207 346), with a weighted estimate of 10 428 (0.06%) pregnant patients with cancer. Individuals with cancer were older, with higher rates of comorbid conditions, than those without cancer. VTE incidence in individuals with cancer at 42 and 330 days was 1.11% and 2.19%, respectively, vs 0.11% and 0.14%, respectively, in those without cancer. At 330 days, this finding was significant in both unadjusted (relative risk, 15.52; 95% CI, 11.54-19.51) and adjusted (relative risk, 9.68; 95% CI, 7.18-12.18) models. Stratification by cancer type and delivery route demonstrated elevated VTE risk across cancer types, with cesarean delivery conferring a greater risk.

CONCLUSION

Cancer in pregnancy confers excess thromboembolic risk extending beyond the immediate postpartum period. Further study is needed to identify optimal VTE prophylactic strategies for this population.

Efficacy of Postpartum Pharmacologic Thromboprophylaxis: A Systematic Review and Meta-analysis

OBJECTIVE

To evaluate the effectiveness of pharmacologic venous thromboembolism (VTE) prophylaxis in postpartum patients.

DATA SOURCES

On February 21, 2022, a literature search was conducted on Embase.com, Ovid-Medline All, Cochrane Library, Scopus, and ClinicalTrials.gov using terms postpartum period AND thromboprophylaxis AND antithrombin medications including heparin and low molecular weight heparin.

METHODS OF STUDY SELECTION

Studies that evaluated the outcome of VTE among postpartum patients exposed to pharmacologic VTE prophylaxis with or without a comparator group were eligible for inclusion. Studies of patients who received antepartum VTE prophylaxis, studies in which this prophylaxis could not be definitively ruled out, and studies of patients who received therapeutic dosing of anticoagulation for specific medical problems or treatment of VTE were excluded. Titles and abstracts were independently screened by two authors. Relevant full-text articles were retrieved and independently reviewed for inclusion or exclusion by two authors.

TABULATION, INTEGRATION, AND RESULTS

A total of 944 studies were screened by title and abstract, and 54 full-text studies were retrieved for further evaluation after 890 studies were excluded. Fourteen studies including 11,944 patients were analyzed: eight randomized controlled trials (8,001 patients) and six observational studies (3,943 patients). Among the eight studies with a comparator group, there was no difference in the risk of VTE between patients who were exposed to postpartum pharmacologic VTE prophylaxis and those who were unexposed (pooled relative risk 1.02, 95% CI 0.29-3.51); however, six of eight studies had no events in either the exposed or unexposed group. Among the six studies without a comparator group, the pooled proportion of postpartum VTE events was 0.00, likely due to five of six studies having no events.

CONCLUSION

The current literature provided an insufficient sample size to conclude whether postpartum VTE rates differ between those exposed to postpartum pharmacologic prophylaxis and those unexposed, given the rarity of VTE events.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD42022323841.

A Longitudinal Study of Thrombosis and Bleeding Outcomes With Thromboprophylaxis in Pregnant Women at Intermediate and High Risk of VTE

BACKGROUND

The efficacy and safety of thromboprophylaxis in pregnancy at intermediate to high risk of venous thrombo-embolism (VTE) is an area of ongoing research.

AIM

This study aimed to assess thrombosis and bleeding outcomes associated with thromboprophylaxis in women at risk of VTE.

METHODS

A cohort of 129 pregnancies, who received thromboprophylaxis for the prevention of VTE, were identified from a specialist obstetric clinic in Johannesburg, South Africa. Intermediate-risk pregnancies, with medical comorbidities or multiple low risks, were managed with fixed low-dose enoxaparin antepartum and for a median (interquartile range) of 4 (4) weeks postpartum. High-risk pregnancies, with a history of previous VTE, were managed with anti-Xa adjusted enoxaparin antepartum and for a median of 6 (0) weeks postpartum. Pregnancy-related VTE was objectively confirmed. Major bleeding, clinically relevant nonmajor bleeding (CRNMB) and minor bleeding were defined according to the International Society on Thrombosis and Hemostasis Scientific Subcommittee.

RESULTS

Venous thrombo-embolism occurred antepartum in 1.4% (95% CI: 0.04-7.7) of intermediate and 3.4% (95% CI: 0.4-11.7) of high-risk pregnancies. Bleeding events occurred in 7.1% (95% CI: 2.4-15.9) of intermediate and 8.5% (95% CI: 2.8-18.7) of high-risk pregnancies. Of these bleeding events, 3.1% (95% CI: 1.0-8.0) were classified as major bleeding. On univariate analysis, no independent predictors of bleeding were identified.

CONCLUSION

The rates of thrombosis and bleeding in this predominantly African population were consistent with similar studies and can be used to inform pregnant women of the benefits of anticoagulation and the risks of potential bleeding.

Intermediate-dose versus low-dose low-molecular-weight heparin in pregnant and post-partum women with a history of venous thromboembolism (Highlow study): an open-label, multicentre, randomised, controlled trial

BACKGROUND

Pregnancy-related venous thromboembolism is a leading cause of maternal morbidity and mortality, and thromboprophylaxis is indicated in pregnant and post-partum women with a history of venous thromboembolism. The optimal dose of low-molecular-weight heparin to prevent recurrent venous thromboembolism in pregnancy and the post-partum period is uncertain.

METHODS

In this open-label, randomised, controlled trial (Highlow), pregnant women with a history of venous thromboembolism were recruited from 70 hospitals in nine countries (the Netherlands, France, Ireland, Belgium, Norway, Denmark, Canada, the USA, and Russia). Women were eligible if they were aged 18 years or older with a history of objectively confirmed venous thromboembolism, and with a gestational age of 14 weeks or less. Eligible women were randomly assigned (1:1), before 14 weeks of gestational age, using a web-based system and permuted block randomisation (block size of six), stratified by centre, to either weight-adjusted intermediate-dose or fixed low-dose low-molecular-weight heparin subcutaneously once daily until 6 weeks post partum. The primary efficacy outcome was objectively confirmed venous thromboembolism (ie, deep-vein thrombosis, pulmonary embolism, or unusual site venous thrombosis), as determined by an independent central adjudication committee, in the intention-to-treat (ITT) population (ie, all women randomly assigned to treatment). The primary safety outcome was major bleeding which included antepartum, early post-partum (within 24 h after delivery), and late post-partum major bleeding (24 h or longer after delivery until 6 weeks post partum), assessed in all women who received at least one dose of assigned treatment and had a known end of treatment date. This study is registered with ClinicalTrials.gov, NCT01828697, and is now complete.

FINDINGS

Between April 24, 2013, and Oct 31, 2020, 1339 pregnant women were screened for eligibility, of whom 1110 were randomly assigned to weight-adjusted intermediate-dose (n=555) or fixed low-dose (n=555) low-molecular-weight heparin (ITT population). Venous thromboembolism occurred in 11 (2%) of 555 women in the weight-adjusted intermediate-dose group and in 16 (3%) of 555 in the fixed low-dose group (relative risk [RR] 0·69 [95% CI 0·32-1·47]; p=0·33). Venous thromboembolism occurred antepartum in five (1%) women in the intermediate-dose group and in five (1%) women in the low-dose group, and post partum in six (1%) women and 11 (2%) women. On-treatment major bleeding in the safety population (N=1045) occurred in 23 (4%) of 520 women in the intermediate-dose group and in 20 (4%) of 525 in the low-dose group (RR 1·16 [95% CI 0·65-2·09]).

INTERPRETATION

In women with a history of venous thromboembolism, weight-adjusted intermediate-dose low-molecular-weight heparin during the combined antepartum and post-partum periods was not associated with a lower risk of recurrence than fixed low-dose low-molecular-weight heparin. These results indicate that low-dose low-molecular-weight heparin for thromboprophylaxis during pregnancy is the appropriate dose for the prevention of pregnancy-related recurrent venous thromboembolism.

FUNDING

French Ministry of Health, Health Research Board Ireland, GSK/Aspen, and Pfizer.

PREGNANCY AFTER COMBINED ORAL CONTRACEPTIVE-ASSOCIATED VENOUS THROMBOEMBOLISM: AN INTERNATIONAL RETROSPECTIVE STUDY OF OUTCOMES

BACKGROUND

Few data are available on thrombotic outcomes during pregnancy and puerperium occurring after an initial provoked venous thromboembolic event (VTE).

OBJECTIVES

To describe thrombotic outcomes during pregnancy after a first combined oral contraceptive (COC)-associated VTE and the factors associated with recurrence Methods. This was an international multicentric retrospective study on patients referred for thrombophilia screening from January 1st 2010 to January 1st 2021 following a first COC-associated VTE, including women with neither inherited thrombophilia nor antiphospholipid antibodies and focusing on those who had a subsequent pregnancy under the same thromboprophylaxis treatment. Thrombotic recurrences during pregnancy and puerperium as well as risk factors for recurrence were analysed.

RESULTS

We included 2,145 pregnant women. A total of 88 thrombotic events, 58 antenatal and 29 postnatal, occurred, mostly during the first trimester of pregnancy and the first two weeks of puerperium. Incidence rates were 49.6 (37-62) per 1,000 patient-years during pregnancy and 118.7 (78-159) per 1,000 patient-years during puerperium. Focusing on pulmonary embolism, incidence rates were 1.68 (1-4) per 1,000 patient-years during pregnancy and 65.5 (35-97) per 1,000 patient-years during puerperium. Risk factors for antenatal recurrences were maternal hypercholestorolaemia and birth of a very small-for-gestational-age neonate. A risk factor for postnatal recurrence was the incidence of preeclampsia. Conclusions Our multicentric retrospective data show significant rates of VTE recurrence during pregnancy and puerperium in women with a previous VTE event associated with COC, despite a unique LMWH-based thromboprophylaxis. These results may provide benchmarks and valuable information for designing future randomized controlled trials.

First Trimester Anticoagulant Exposure and Adverse Pregnancy Outcomes in Women with Preconception Venous Thromboembolism: A Nationwide Cohort Study

OBJECTIVE

The purpose of this study was to investigate first trimester anticoagulant exposure and risks of adverse pregnancy-related and fetal outcomes.

METHODS

Using Danish nationwide registries, we identified all pregnant women with preconception venous thromboembolism, 2000-2017, and linked data on exposure to low-molecular-weight heparin (LMWH), vitamin K antagonist (VKA), or non-VKA oral anticoagulant (NOAC) during pregnancy. We assessed pregnancy-related and fetal outcomes associated with first trimester anticoagulant exposure.

RESULTS

Among 4490 pregnancies in women with preconception venous thromboembolism (mean age 31 years, 40% nulliparous) during the first trimester, 63.1% were unexposed, 25.9% were exposed to LMWH, 10.4% VKA, and 0.6% NOAC. Adverse outcomes were lowest in unexposed and LMWH exposed. Compared with unexposed, VKA was associated with higher risks of preterm (adjusted odds ratio [OR] 2.26; 95% confidence interval [CI], 1.70-2.99) and very preterm birth (adjusted OR 3.78; 95% CI, 1.91-7.49), shorter mean gestational age was associated with VKA (-7.5 days; 95% CI, -9.1 to -5.9 days) or NOAC (-2.3 days; 95% CI, -8.4-3.8), and lower mean birthweight with VKA (-55 g; 95% CI, -103.1 to -8.5) or NOAC (-190 g; 95% CI, -364.1 to -16.4). Adjusted ORs for small-for-gestational-age infants were 1.07 (95% CI, 0.77-1.50) with VKA, and 3.29 (95% CI, 1.26-7.95) with NOAC. Mean 5-minute Apgar score (9.8) and congenital defect prevalence (8.4%-10%) varied little across exposure groups.

CONCLUSIONS

Fetal risk was lowest in unexposed and LMWH-exposed pregnancies, supporting the recommendation of LMWH during pregnancy. NOAC safety during pregnancy is unclear due to the rarity of NOAC exposure.

Risk factors for recurrence during a pregnancy following a first venous thromboembolism: A French observational study

BACKGROUND

Women with a previous venous thromboembolism (VTE) are at risk of recurrence during pregnancy.

OBJECTIVES

We aimed to assess the incidence rate of recurrent VTE during pregnancy, according to the period of pregnancy, and the clinical parameters associated with recurrence, in a prospective cohort of women of childbearing age after a first VTE.

PATIENTS/METHODS

A total of 189 women aged 15-49 years with a first documented VTE were followed until a subsequent pregnancy of at least 20 weeks' gestation between 2000 and 2020. VTE recurrences during pregnancy were recorded, as were potential clinical risk factors for recurrence.

RESULTS

Recurrent VTE occurred in six women during antepartum: five during the first trimester (incidence rate 106.4 per 1000 women-years) (95% confidence interval [CI] 46.3-226.0); none during the second trimester; and one during the third trimester (incidence rate 27.0 per 1000 women-years [95% CI 4.8-138.2]). During postpartum, recurrences occurred in 11 women (incidence rate 212.8 per 1000 women-years [95% CI 119.9-349.1]). These 17 recurrent VTEs presented as pulmonary embolism ± deep vein thrombosis (DVT) in five patients and isolated DVT in 12. Failure of thromboprophylaxis occurred in two cases (33.3%) antepartum and in 10 cases (90.9%) postpartum. In multivariable analysis, only obesity (defined on prepregnancy body mass index) was associated with recurrent VTE (odds ratio 3.34 [95% CI 1.11-10.05, p = .03]).

CONCLUSIONS

This study confirms a high risk of recurrent VTE postpartum, despite thromboprophylaxis, in women with a previous VTE. Only obesity was associated with VTE recurrence during pregnancy, suggesting that low-dose anticoagulation might not be appropriate in obese pregnant women.

Thrombophilia, Thrombosis and Thromboprophylaxis in Pregnancy: For What and in Whom?

Compared with nonpregnant women, pregnancy carries a four- to fivefold higher risk of venous thromboembolism (VTE). Despite increasing use of heparin prophylaxis in identified high-risk patients, pulmonary embolism still is the leading cause of maternal mortality in the western world. However, evidence on optimal use of thromboprophylaxis is scarce. Thrombophilia, the hereditary or acquired tendency to develop VTE, is also thought to be associated with complications in pregnancy, such as recurrent miscarriage and preeclampsia. In this review, the current evidence on optimal thromboprophylaxis in pregnancy is discussed, focusing primarily on VTE prevention strategies but also discussing the potential to prevent recurrent pregnancy complications with heparin in pregnant women with thrombophilia.

Prophylactic Anticoagulation With Intermediate-Dose Certoparin in Vascular-Risk Pregnancies-The PACER-VARP Registry

The management of pregnant women at increased risk of thromboembolic/other vascular events is still a matter of debate. In a single-center, retrospective, observational trial, we analyzed the safety and efficacy of prophylactic anticoagulation with certoparin in pregnant women at intermediate- or high-risk by EThIG criteria of thromboembolic/other vascular events. Subcutaneous certoparin 8,000 IU once daily was administered immediately after pregnancy confirmation and continued for 6 weeks postpartum. We investigated 74 pregnancies (49 women; mean age 31.8 years; weight 77.3 kg). Most prevalent risk factors were factor V Leiden mutation (40.5%), thrombogenic factor II mutation (12.2%) and protein S deficiency (8.1%). In 76 control pregnancies prior to registry inclusion/without anticoagulation there were 14 cases [18.4%] of venous thromboembolism (between week 7 gestation and week 8 postpartum); 63.2% pregnancies resulted in abortion (median week 8.6 gestation). With certoparin anticoagulation, thromboembolism was 1.4%, exclusively non-major bleeding was 4.1% and abortion was 10.8%. One case of pre-eclampsia necessitating obstetric intervention occurred. Prophylactic anticoagulation with intermediate-dose certoparin throughout pregnancies at increased venous vascular risk was safe and effective.

Maternal and perinatal outcomes of a venous thromboembolism high-risk cohort using a multidisciplinary treatment approach

OBJECTIVE

To evaluate the maternal and perinatal outcomes in a cohort of pregnant women at high risk of venous thromboembolism (VTE).

METHODS

Women at high risk of VTE were evaluated in a multidisciplinary program using a complete diagnostic workup, and specific prophylactic or therapeutic treatment.

RESULTS

Women were considered at high risk of VTE in 57% (85/148) because of prior (75) or current (10) thromboembolism, and in 27% (40/148) of the cases due to adverse obstetric history. Thrombophilia was diagnosed in 57% of the cases (85/148), either in patients with previous thromboembolism (48%, 41/85) or without a history of thrombosis (70%, 44/63). The most common thrombophilia was antiphospholipid syndrome in 34% (29/85) of the cases. Under respective prophylactic or therapeutic treatment, there were no VTE during pregnancy (0%, 0/148), whereas four events occurred during the puerperium (3%, 4/148). An adverse obstetric outcome was present in 5% (7/148) of all pregnancies, with four early spontaneous abortions (3%, 4/148) and three late miscarriages (2%, 3/148).

CONCLUSION

Pregnant women at high risk of VTE can be effectively managed using a risk-adapted treatment. Our results support prospective enrollment and a multidisciplinary assessment of VTE in high-risk pregnant women.

Pulmonary Embolism in Pregnancy

Even though venous thromboembolism is a leading cause of maternal mortality in high-income countries, there are limited high-quality data to assist clinicians with the management of pulmonary embolism in this patient population. Diagnosis, prevention, and treatment of pregnancy-associated pulmonary embolism are complicated by the need to consider fetal, as well as maternal, well-being. Recent studies suggest that clinical prediction rules and D-dimer testing can reduce the need for diagnostic imaging in a subset of patients. Low-molecular-weight heparin is the preferred anticoagulant for both prophylaxis and treatment in this setting. Direct oral anticoagulants are contraindicated during pregnancy and in breastfeeding women. Thrombolysis or embolectomy should be considered for pregnant women with pulmonary embolism complicated by hemodynamic instability. Treatment of pregnancy-associated pulmonary embolism should be continued for at least 3 months, including 6 weeks postpartum. Management of anticoagulants at the time of delivery should involve a multidisciplinary individualized approach that uses shared decision making to take patient and caregiver values and preferences into account.

Prophylactic anticoagulation for preterm premature rupture of membranes: a decision analysis

BACKGROUND

The current standard of care in the setting of preterm premature rupture of membranes involves antenatal hospitalization until delivery. The reduced physical activity during this time compounds the heightened risk for venous thromboembolism in pregnancy. Prophylactic anticoagulation can decrease this risk of venous thromboembolism; however, this benefit must be balanced against the risks of precluding neuraxial analgesia or increasing the risk of postpartum hemorrhage.

OBJECTIVE

The objective of this study was to determine the optimal modality for venous thromboembolism prophylaxis during hospitalization for preterm premature rupture of membranes using a decision analysis model.

STUDY DESIGN

A decision-analytical Markov model was constructed using the TreeAge software comparing the use of unfractionated heparin, low-molecular-weight heparin or no anticoagulation in women with a singleton pregnancy who were hospitalized for preterm premature rupture of membranes after 24 weeks and remained hospitalized until delivery. Maternal outcomes examined included attainment of neuraxial analgesia (vs no analgesia for vaginal delivery or general anesthesia for cesarean delivery), venous thromboembolism, postpartum hemorrhage, and maternal death. Probabilities and utilities were derived from existing literature. Sensitivity analyses were performed to interrogate model assumptions, and a Monte Carlo probabilistic sensitivity analysis was performed to examine the robustness of the model.

RESULTS

In this decision-analytical model, no prophylactic anticoagulation maximized maternal utilities. Clinical outcomes among a theoretical cohort of 100,000 women are shown in the Table. The 1- and 2-way sensitivity analyses supported this conclusion. Monte Carlo probabilistic sensitivity analysis indicated that no prophylaxis was the preferred choice in 56% of simulations, unfractionated heparin in 34% of simulations, and low-molecular-weight heparin in 10% of simulations.

CONCLUSION

Our results do not support the routine use of prophylactic anticoagulation in women admitted to the hospital for preterm premature rupture of membranes. These findings can be used to inform clinical decisions when admitting low-risk singleton pregnancies to the hospital in the setting of preterm premature rupture of membranes.

Venous thromboembolism risk and prophylaxis in hospitalized obstetric patients at a tertiary hospital in Accra, Ghana: A comparative cross-sectional study

OBJECTIVE

To determine the prevalence of venous thromboembolism risk and thromboprophylaxis among obstetric inpatients, comparing prenatal and postnatal women.

METHODS

We assessed 546 obstetric inpatients at the Korle-Bu Teaching Hospital for the prevalence study. Out of this number, 223 were recruited, comprising 111 prenatal and 112 postnatal mothers. A structured interviewer-administered questionnaire was used to obtain data on participants' venous thromboembolism risk, which was categorized into high, intermediate, and low using the Royal College of Obstetricians and Gynaecologists guidelines. Data on thromboprophylaxis were also obtained and analyzed. Values were considered statistically significant at p < 0.05.

RESULTS

Overall venous thromboembolism risk among the study population was 82/223 (36.8%). All patients at high risk were prenatal, 59/112 (52.7%) of postnatal mothers were at intermediate risk, compared with 20/111 (18.0%) of prenatal women (p < 0.001). Prevalence of thromboprophylaxis was 5/82 (6.1%). All prenatal high-risk patients received thromboprophylaxis, whereas only 2/20 (10.0%) of women with intermediate risk received thromboprophylaxis. The incidence of venous thromboembolism was 3/546 (0.6%) in the obstetric inpatients.

CONCLUSION

Our study found a high prevalence of venous thromboembolism risk among obstetric inpatients at the Korle-Bu Teaching Hospital. However, thromboprophylaxis was low. Further research is needed to audit recent practice of thromboprophylaxis and perinatal outcome.

VTE risk assessment in pregnancy

A State of the Art lecture, "VTE Risk Assessment in Pregnancy," was presented at the ISTH congress in Melbourne, Australia, in 2019. Venous thromboembolism (VTE) remains a leading cause of death in pregnancy and in the postpartum period. Moreover, VTE can result in lifelong disability. The elevated baseline pregnancy-associated VTE risk is further increased by additional maternal, pregnancy, and delivery characteristics, highlighting the importance of VTE risk assessment in early pregnancy, at delivery, and if risk factors change. This review will provide an overview of the impact and epidemiology of VTE in pregnancy (including reported risk factors for pregnancy-associated VTE), will address VTE risk-reduction strategies (including ongoing studies), and will provide a summary of critical knowledge gaps. Finally, throughout this review, relevant new data presented during the 2019 ISTH annual congress in Melbourne will be summarized.

American Society of Hematology 2018 guidelines for management of venous thromboembolism: venous thromboembolism in the context of pregnancy

BACKGROUND

Venous thromboembolism (VTE) complicates ∼1.2 of every 1000 deliveries. Despite these low absolute risks, pregnancy-associated VTE is a leading cause of maternal morbidity and mortality.

OBJECTIVE

These evidence-based guidelines of the American Society of Hematology (ASH) are intended to support patients, clinicians and others in decisions about the prevention and management of pregnancy-associated VTE.

METHODS

ASH formed a multidisciplinary guideline panel balanced to minimize potential bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline development process, including updating or performing systematic evidence reviews. The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess evidence and make recommendations.

RESULTS

The panel agreed on 31 recommendations related to the treatment of VTE and superficial vein thrombosis, diagnosis of VTE, and thrombosis prophylaxis.

CONCLUSIONS

There was a strong recommendation for low-molecular-weight heparin (LWMH) over unfractionated heparin for acute VTE. Most recommendations were conditional, including those for either twice-per-day or once-per-day LMWH dosing for the treatment of acute VTE and initial outpatient therapy over hospital admission with low-risk acute VTE, as well as against routine anti-factor Xa (FXa) monitoring to guide dosing with LMWH for VTE treatment. There was a strong recommendation (low certainty in evidence) for antepartum anticoagulant prophylaxis with a history of unprovoked or hormonally associated VTE and a conditional recommendation against antepartum anticoagulant prophylaxis with prior VTE associated with a resolved nonhormonal provoking risk factor.

Sex matters: Practice 5P's when treating young women with venous thromboembolism

Sex matters when it comes to venous thromboembolism (VTE). We defined 5P's - period, pill, prognosis, pregnancy, and postthrombotic syndrome - that should be discussed with young women with VTE. Menstrual blood loss (Period) can be aggravated by anticoagulant therapy. This seems particularly true for direct oral anticoagulants. Abnormal uterine bleeding can be managed by hormonal therapy, tranexamic acid, or modification of treatment. The use of combined oral contraceptives (Pill) is a risk factor for VTE. The magnitude of the risk depends on progestagen types and estrogen doses used. In women using therapeutic anticoagulation, concomitant hormonal therapy does not increase the risk of recurrent VTE. Levonorgestrel-releasing intrauterine devices and low-dose progestin-only pills do not increase the risk of VTE. In young women VTE is often provoked by transient hormonal risk factors that affects prognosis. Sex is incorporated as predictor in recurrent VTE risk assessment models. However, current guidelines do not propose using these to guide treatment duration. Pregnancy increases the risk of VTE by 4-fold to 5-fold. Thrombophilia and obstetric risk factors further increase the risk of pregnancy-related VTE. In women with a history of VTE, the risk of recurrence during pregnancy or post partum appears to be influenced by risk factors present during the first VTE. In most women with a history of VTE, antepartum and postpartum thromboprophylaxis with low-molecular-weight heparin is indicated. Women generally are affected by VTE at a younger age then men, and they have to deal with long-term complications (Post-thrombotic syndrome) of deep vein thrombosis early in life.

Comparison of 2 approaches in management of pregnant women with inherited trombophilias: Prospective analytical cohort study

Previous adverse pregnancy outcomes (APO) in women with hereditary thrombophilia have emerged as new indications for prophylactic use of low-molecular-weight heparin (LMWH) during pregnancy. Recent meta-analysis conducted to establish if LMWH may prevent recurrent placenta-mediated pregnancy complications point to important therapeutic effect but these findings are absolutely not universal. Furthermore, previous studies regarding LMWH prophylaxis for APO in women with inherited thrombophilia were performed in high risk patients with previous adverse health outcomes in medical, family and/or obstetric history. Therefore, the aim of this study was to investigate the effects of LMWH prophylaxis on pregnancy outcomes in women with inherited thrombophilias regardless of the presence of previous adverse health outcomes in medical, family, and obstetric history.Prospective analytical cohort study included all referred women with inherited thrombophilia between 11 and 15 weeks of gestation and followed-up to delivery. Patients were allocated in group with LWMH prophylaxis (study group) and control group without LWMH prophylaxis. The groups were compared for laboratory parameters and Doppler flows of umbilical artery at 28 to 30th, 32nd to 34th and 36th to 38th gestational weeks (gw), and for obstetric and perinatal outcomes.The study group included 221 women and control group included 137 women. Mean resistance index of the umbilical artery Ri in 28 to 30, 32 to 34, and 36 to 38 gw were significantly higher in the control group compared to study group (0.71 ± 0.02 vs 0.69 ± 0.02; 0.67 ± 0.03 vs 0.64 ± 0.02; and 0.67 ± 0.05 vs 0.54 ± 0.08, respectively). Intrauterine fetal death (IUFD) and miscarriages were statistically significantly more frequent in control group compared to the patients in study (P < .001). The frequencies of fetal growth restriction (FGR) and APO were significantly higher in the control group compared to the study group (P = .008 and P < .001, respectively). In a multivariate regression model with APO as a dependent variable, only Ri was detected as a significant protective factor for APO, after adjusting for age and LMWH prophylaxis (P < .001).We have demonstrated better perinatal outcomes in women with LMWH prophylaxis for APO compared to untreated women.

Effectiveness and safety of thromboprophylaxis with enoxaparin for prevention of pregnancy-associated venous thromboembolism

Essentials Thromboprophylaxis is offered to women considered to be at risk from pregnancy-associated venous thromboembolism (PA-VTE) but there is a suggestion that standard doses of low-molecular-weight heparin may not be effective. We conducted a large observational cohort study reviewing maternal outcomes in women who received extended thromboprophylaxis with enoxaparin for prevention of PA-VTE. We report a low rate of breakthrough VTE in women, the majority of whom received standard doses of enoxaparin. High rates of postpartum hemorrhage are reported in our cohort. Our data do not strongly support a move to increase doses of thromboprophylaxis for prevention of PA-VTE and raise the possibility that higher doses may increase bleeding complications and limit women's access to neuraxial analgesia/anesthesia.

BACKGROUND

Low-molecular-weight heparin is used to prevent pregnancy-associated venous thromboembolism (PA-VTE), but there are limited data to inform which women require thromboprophylaxis in pregnancy and debate about which low-molecular-weight heparin dose is effective and safe.

AIMS

To evaluate the efficacy and rate of complications using enoxaparin for thromboprophylaxis in a cohort of women at risk of PA-VTE managed between 1999 and 2014 at National Women's Hospital, a tertiary obstetric referral center in Auckland, New Zealand.

METHODS

A retrospective, observational study of women who received thromboprophylaxis with enoxaparin for prevention of PA-VTE while under the care of the obstetric or maternal fetal medicine team.

RESULTS

A total of 172 pregnancies in 123 women were identified. A single daily dose of 40 mg enoxaparin was used in 94.8% of pregnancies. Two breakthrough PA-VTEs occurred (1.2% [95% confidence interval, 0.32-4.14]). Postpartum hemorrhage ≥500 mL was reported in 36.6% of births and postpartum hemorrhage ≥1000 mL in 9.3% of births. Only four women were transfused. Neuraxial analgesia/anesthesia was used in 52.4% of births, including 39.6% of vaginal births.

CONCLUSION

Use of standard doses enoxaparin thromboprophylaxis in our cohort was effective at preventing PA-VTE. Neuraxial analgesia/anesthesia was used frequently during labor and birth;, using higher doses of enoxaparin may limit access to this. Postpartum hemorrhage was common and higher doses of thromboprophylaxis may increase obstetric bleeding complications. These data do not suggest an urgent need to consider higher doses of enoxaparin for thromboprophylaxis in this clinical setting.

Safety and efficacy of adjusted-dose enoxaparin in pregnant patients with increased risk for venous thromboembolic disease

OBJECTIVE

To assess the efficacy and safety of anti-Xa guided dose-adjusted low molecular weight heparin (LMWH) thromboprophylaxis in at-risk pregnant women.

METHODS

This single-center retrospective study was conducted at a quaternary hospital in Johannesburg, South Africa. We analyzed clinical and laboratory data for pregnant patients referred between January 1, 1999, and May 1, 2017, with an increased risk of venous thromboembolic disease (VTED) and treated with prophylactic LMWH adjusted according to anti-Xa levels. The efficacy endpoint was pregnancy-related VTED and/or pregnancy loss despite anti-Xa guided dose-adjusted LMWH thromboprophylaxis.

RESULTS

We reviewed data for 113 consecutive pregnant patients with 151 pregnancies referred for prophylactic LMWH. Prevalence of pregnancy-related VTED was 1.3% (95% confidence interval [CI] 0.1-4.7), which is lower than that reported in the literature for fixed-dose thromboprophylaxis in similar at-risk groups. One venous thromboembolism event occurred in the antenatal period (despite adequate prophylaxis) and the second in the postpartum period (related to prolonged labor). Prevalence of pregnancy-related bleeding was 2% (95% CI 0.4-5.7) with all bleeding events considered to be minor and unrelated to LMWH therapy.

CONCLUSION

This study demonstrated the efficacy and safety of anti-Xa dose-adjusted LMWH thromboprophylaxis in at-risk pregnant patients.

Thromboprophylaxis in Pregnancy

Venous thromboembolism is a leading cause of maternal morbidity and mortality worldwide. Identifying women who are at greatest risk for venous thromboembolism, and managing their pregnancies with appropriate thromboprophylaxis is essential to decreasing this life-threatening condition. Those at greatest risk are patients with thrombophilias, a personal or family history of venous thromboembolism, and those undergoing cesarean delivery. Current international guidelines on thromboprophylaxis vary in details, but all strategies rely on risk factor identification and thromboprophylaxis for the highest risk patients. All guidelines require clinicians to think critically about individual patient's risk factors throughout pregnancy and the postpartum period.

Preventing venous thromboembolism during pregnancy and postpartum: crossing the threshold

When should a patient with a known thrombophilia or prior venous thromboembolism (VTE) receive low-molecular-weight heparin (LMWH) prophylaxis during pregnancy and/or the postpartum period? Accurately predicting thrombotic and bleeding risks and knowing what to do with this information is at the heart of decision-making in these challenging scenarios. This article will explore the concept of a risk threshold from clinician and patient perspectives and provide guidance for the use of antepartum and postpartum LMWH prophylaxis in women with a known thrombophilia or prior VTE. Advice for the management of LMWH prophylaxis use around labor and delivery is also reviewed.

Obstetric complications and pregnancy-related venous thromboembolism: The effect of low-molecular-weight heparin on their prevention in carriers of factor V Leiden or prothrombin G20210A mutation

Whether the administration of low-molecular-weight heparin (LMWH) during pregnancy is effective in preventing obstetric complications and pregnancy-related venous thromboembolism (VTE) in women who are carriers of factor V Leiden (FVL) and/or prothrombin variant G20210A (PTm) is controversial. This observational study investigated the possible efficacy of pharmacological treatment with LMWH ± aspirin (ASA) in pregnancy outcomes in 1,011 pregnancies of 416 women with thrombophilia (FVL and/or PTm). Most patients were chosen on the basis of previous obstetrical complications (36%), or because of familial or personal history of venous/arterial thromboembolism (28% and 18%, respectively); 74 patients (18%) were incidentally identified. The outcome was evaluated according to the type of treatment and of the period of pregnancy when the treatment was started. After adjustment for observation before and after diagnosis of thrombophilia, previous miscarriages and VTE, parity, age and centre, we observed that LMWH had a protective effect on miscarriages (odds ratio [OR] 0.52, 95% confidence interval [CI] 0.29–0.94) and VTE (OR 0.05, 95% CI 0.01–0.21). ASA appeared to have no effect on the prevention of obstetric complications and VTE. A nested analysis performed in 116 women with two or more obstetric complications confirmed that the highest number of live births was recorded in the group under LMWH prophylaxis (OR 0.19, 95% CI 0.05–0.75). These results suggest that LMWH prophylaxis reduces the risk of obstetric complications in carriers of FVL and/or PTm, particularly in those with previous obstetric events. Furthermore, LMWH prophylaxis reduces the risk of pregnancy-related VTE.

Thrombin generation and low-molecular-weight heparin prophylaxis in pregnant women with thrombophilia

Pregnancy is associated with increased risk of venous thromboembolism, especially in the presence of thrombophilia. However, there is no consensus on the optimal approach for thromboprophylaxis in this population. Recent evidence suggests that thrombin generation correlates with the overall procoagulant state of the plasma. Our aim was to evaluate thrombin generation in a prospective cohort of thrombophilic pregnant women, and investigate the effectiveness of low-molecular- weight heparin (LMWH) prophylaxis in pregnancy. Women with severe (n=8), mild (n=47) and no (n=15) thrombophilia were followed throughout their pregnancies. Thrombin generation was evaluated in each trimester as well as five days and eight weeks postpartum (as a reference category). In women undergoing LMWH prophylaxis, thrombin generation and anti-Factor-Xa activity were measured just before and 4 hours after administration (peak effect). Thrombin generation was determined using Technothrombin TGA assay system. For the analysis, median peak thrombin and endogenous thrombin potential were used. Peak thrombin and endogenous thrombin potential were increased during pregnancy compared to the non-pregnant state with the highest results in the severe thrombophilia group. In women receiving LMWH prophylaxis a decrease was observed in thrombin generation at peak effect but over the progression of pregnancy the extent of this decrease reduced in a stepwise fashion. Our results show that thrombin generation demonstrates the hypercoagulable state in thrombophilic pregnancies. In addition, we found the effect of LMWH prophylaxis to progressively decrease with advancing stages of pregnancy.

Pregnancy, thrombophilia, and the risk of a first venous thrombosis: systematic review and bayesian meta-analysis

Objective To provide evidence to support updated guidelines for the management of pregnant women with hereditary thrombophilia in order to reduce the risk of a first venous thromboembolism (VTE) in pregnancy.Design Systematic review and bayesian meta-analysis.Data sources Embase, Medline, Web of Science, Cochrane Library, and Google Scholar from inception through 14 November 2016.Review methods Observational studies that reported on pregnancies without the use of anticoagulants and the outcome of first VTE for women with thrombophilia were eligible for inclusion. VTE was considered established if it was confirmed by objective means, or when the patient had received a full course of a full dose anticoagulant treatment without objective testing. Results 36 studies were included in the meta-analysis. All thrombophilias increased the risk for pregnancy associated VTE (probabilities ≥91%). Regarding absolute risks of pregnancy associated VTE, high risk thrombophilias were antithrombin deficiency (antepartum: 7.3%, 95% credible interval 1.8% to 15.6%; post partum: 11.1%, 3.7% to 21.0%), protein C deficiency (antepartum: 3.2%, 0.6% to 8.2%; post partum: 5.4%, 0.9% to 13.8%), protein S deficiency (antepartum: 0.9%, 0.0% to 3.7%; post partum: 4.2%; 0.7% to 9.4%), and homozygous factor V Leiden (antepartum: 2.8%, 0.0% to 8.6%; post partum: 2.8%, 0.0% to 8.8%). Absolute combined antepartum and postpartum risks for women with heterozygous factor V Leiden, heterozygous prothrombin G20210A mutations, or compound heterozygous factor V Leiden and prothrombin G20210A mutations were all below 3%. Conclusions Women with antithrombin, protein C, or protein S deficiency or with homozygous factor V Leiden should be considered for antepartum or postpartum thrombosis prophylaxis, or both. Women with heterozygous factor V Leiden, heterozygous prothrombin G20210A mutation, or compound heterozygous factor V Leiden and prothrombin G20210A mutation should generally not be prescribed thrombosis prophylaxis on the basis of thrombophilia and family history alone. These data should be considered in future guidelines on pregnancy associated VTE risk.

Prophylaxis for Venous Thromboembolism

Venous thromboembolisms are major risk factors for many of our hospitalized patients. These events, however, can be prevented with prophylactic measurements when administered appropriately and on a timely basis. As patients are admitted, discharged, transferred, and scheduled for procedures on an hourly basis, anticoagulation and deep vein thrombosis prophylaxis are held or discontinued in anticipation for possible procedures. This results in delay of care and intervals where patients may not be covered with any prophylactic measurements. Similarly, alterations in clinical status can quickly change such as an increase in creatinine levels or the development of a new bleed, thus requiring a revision in their deep vein thrombosis prophylaxis. Nurses, therefore, play an integral role in not only administering the medicine but also routinely assessing the patients' clinical status and, therefore, their deep vein thrombosis prophylactic regimens as well. This article will review the indications, scoring systems, common prophylactic methods, and special populations at increased risks for venous thromboembolisms.

Guidance for the treatment of deep vein thrombosis and pulmonary embolism

This guidance document focuses on the diagnosis and treatment of venous thromboembolism (VTE). Efficient, cost effective diagnosis of VTE is facilitated by combining medical history and physical examination with pre-test probability models, D dimer testing and selective use of confirmatory imaging. Clinical prediction rules, biomarkers and imaging can be used to tailor therapy to disease severity. Anticoagulation options for acute VTE include unfractionated heparin, low molecular weight heparin, fondaparinux and the direct oral anticoagulants (DOACs). DOACs are as effective as conventional therapy with LMWH and vitamin K antagonists. Thrombolytic therapy is reserved for massive pulmonary embolism (PE) or extensive deep vein thrombosis (DVT). Inferior vena cava filters are reserved for patients with acute VTE and contraindications to anticoagulation. Retrievable filters are strongly preferred. The possibility of thoracic outlet syndrome and May-Thurner syndrome should be considered in patients with subclavian/axillary and left common iliac vein DVT, respectively in absence of identifiable triggers. The optimal duration of therapy is dictated by the presence of modifiable thrombotic risk factors. Long term anticoagulation should be considered in patients with unprovoked VTE as well as persistent prothrombotic risk factors such as cancer. Short-term therapy is sufficient for most patients with VTE associated with transient situational triggers such as major surgery. Biomarkers such as D dimer and risk assessment models such the Vienna risk prediction model offer the potential to customize VTE therapy for the individual patient. Insufficient data exist to support the integration of bleeding risk models into duration of therapy planning.

Low-molecular-weight heparin to prevent recurrent venous thromboembolism in pregnancy: Rationale and design of the Highlow study, a randomised trial of two doses

BACKGROUND

Women with a history of venous thromboembolism (VTE) have a 2% to 10% absolute risk of VTE recurrence during subsequent pregnancies. Therefore, current guidelines recommend that all pregnant women with a history of VTE receive pharmacologic thromboprophylaxis. The optimal dose of low-molecular-weight heparin (LMWH) for thromboprophylaxis is unknown. In the Highlow study (NCT 01828697; www.highlowstudy.org), we compare a fixed low dose of LMWH with an intermediate dose of LMWH for the prevention of pregnancy-associated recurrent VTE. We present the rationale and design features of this study.

METHODS

The Highlow study is an investigator-initiated, multicentre, international, open-label, randomised trial. Pregnant women with a history of VTE and an indication for ante- and postpartum pharmacologic thromboprophylaxis are included before 14weeks of gestation. The primary efficacy outcome is symptomatic recurrent VTE during pregnancy and 6weeks postpartum. The primary safety outcomes are clinically relevant bleeding, blood transfusions before 6weeks postpartum and mortality. Patients are closely monitored to detect cutaneous reactions to LMWH and are followed for 3months after delivery. A central independent adjudication committee adjudicates all suspected outcome events.

CONCLUSION

The Highlow study is the first large randomised controlled trial in pregnancy that will provide high-quality evidence on the optimal dose of LWMH thromboprophylaxis for the prevention of recurrent VTE in pregnant women with a history of VTE.

Guidance for the treatment and prevention of obstetric-associated venous thromboembolism

Venous thromboembolism (VTE), which may manifest as pulmonary embolism (PE) or deep vein thrombosis (DVT), is a serious and potentially fatal condition. Treatment and prevention of obstetric-related VTE is complicated by the need to consider fetal, as well as maternal, wellbeing when making management decisions. Although absolute VTE rates in this population are low, obstetric-associated VTE is an important cause of maternal morbidity and mortality. This manuscript, initiated by the Anticoagulation Forum, provides practical clinical guidance on the prevention and treatment of obstetric-associated VTE based on existing guidelines and consensus expert opinion based on available literature where guidelines are lacking.

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.

New studies of low-molecular-weight heparin in pregnancy

Several aspects of the diagnostic and therapeutic management of women with venous thrombosis are uncertain, because of the absence of adequately sized observational or intervention studies. Here, I will discuss the rationale and design of two currently ongoing investigator-initiated, international, randomized controlled trials of LMWHin pregnancy. The Highlow study (www.highlowstudy.org; NCT Clinicaltrials.gov) 01828697) investigates two doses of low-molecular-weight heparin to prevent recurrent venous thromboembolism (VTE) in pregnant women with a history of VTE. The ALIFE2 study (www.alife2study.org; www.trialregister.nl, NTR 3361) investigates the effect of LMWH on live birth in women with inherited thrombophilia and two or more miscarriages.

Pregnancy and venous thromboembolism: 'TIPPS' for risk stratification

Pregnancy-associated venous thromboembolism (VTE) is a leading cause of maternal mortality, but is relatively uncommon. It is clear that the antepartum and postpartum periods have different magnitudes of risk and distinct risk factors for VTE and therefore must be considered separately. Absolute daily risks of VTE must be understood and explored when deciding to prescribe antepartum or postpartum thromboprophylaxis and must also be balanced against the downsides of prophylaxis. When the risks for VTE and bleeding are both low, other burdens of thromboprophylaxis must be weighed in and a decision made after an individualized patient values- and patient preferences-based discussion. Risk stratification is essential to ensure that the practicing clinician strikes the right balance.

ESHRE Capri Workshop Group. Venous thromboembolism in women: a specific reproductive health risk

BACKGROUND Venous thromboembolism (VTE) is a specific reproductive health risk for women. METHODS Searches were performed in Medline and other databases. The selection criteria were high-quality studies and studies relevant to clinical reproductive medicine. Summaries were presented and discussed by the European Society of Human Reproduction and Embryology Workshop Group. RESULTS VTE is a multifactorial disease with a baseline annual incidence around 50 per 100 000 at 25 years and 120 per 100 000 at age 50. Its major complication is pulmonary embolism, causing death in 1-2% of patients. Higher VTE risk is associated with an inherited thrombophilia in men and women. Changes in the coagulation system and in the risk of clinical VTE in women also occur during pregnancy, with the use of reproductive hormones and as a consequence of ovarian stimulation when hyperstimulation syndrome and conception occur together. In pregnancy, the risk of VTE is increased ~5-fold, while the use of combined hormonal contraception (CHC) doubles the risk and this relative risk is higher with the more recent pills containing desogestrel, gestodene and drospirenone when compared with those with levonorgestrel. Similarly, hormone replacement therapy (HRT) increases the VTE risk 2- to 4-fold. There is a synergistic effect between thrombophilia and the various reproductive risks. Prevention of VTE during pregnancy should be offered to women with specific risk factors. In women who are at high risk, CHC and HRT should be avoided. CONCLUSIONS Clinicians managing pregnancy or treating women for infertility or prescribing CHC and HRT should be aware of the increased risks of VTE and the need to take a careful medical history to identify additional co-existing risks, and should be able to diagnose VTE and know how to approach its prevention.