Incidence of postpartum haemorrhage in women receiving therapeutic doses of low-molecular-weight heparin: results of a retrospective cohort study

Bleeding in women with venous thromboembolism during pregnancy: A systematic review of the literature

Objectives

Venous thromboembolism (VTE) represents an important cause of maternal morbidity and mortality. Estimates of bleeding associated with therapeutic‐dose anticoagulation are variable. We describe the frequency of bleeding in pregnant women receiving therapeutic anticoagulation for VTE by means of a systematic review of the literature.

Data Sources

Medical Literature Analysis and Retrieval System, Embase, Scopus, Web of Science, and ClinicalTrials.gov were searched. Databases were searched from inception to February 27, 2022. There was no language or geographic location restriction.

Methods of Study Selection

The search yielded 2773 articles with 2212 unique citations. Studies were included if they described pregnant women treated for an acute VTE with therapeutic‐dose anticoagulation and a defined bleeding outcome was reported.

Tabulation, Integration, and Results

Five studies met inclusion criteria. Included studies were judged to have a serious to critical risk of bias using the Risk of Bias in Nonrandomized Studies of Intervention tool. The rate of bleeding, as defined by respective studies, ranged between 2.9% and 30.0%. Two studies included control groups, one of which found no significant difference in the risk of bleeding between groups, while the other found a significantly increased bleeding risk associated with therapeutic anticoagulation.

Conclusion

Among pregnant women anticoagulated for VTE, the reported bleeding risk is variable. The ability to draw definite conclusions is limited by the scarcity and low quality of the studies, the small number of included patients, and the heterogeneity of bleeding definitions used. Large‐scale studies with standardized bleeding definitions are required to provide acute bleeding estimates and optimize the care of these patients.

Systematic Review Registration

PROSPERO, CRD42021276771.

Venous thromboembolism during pregnancy and postpartum period

Venous thromboembolism (VTE) is one of the leading causes of maternal mortality. Rates of VTE during pregnancy and the postpartum period have not decreased over the past two decades and pregnancyassociated VTE continues to pose a significant health challenge. Pregnant and postpartum women are at a higher risk for VTE owing to many factors. There are hormonally mediated and pregnancy-specific alterations of coagulation that favor thrombosis, including increased production of clotting factors. There are physiologic and anatomic mechanisms that also contribute, including a decreased rate of venous blood flow from the lower extemities as pregnancy progresses. Cesarean delivery also introduces VTE risk. In addition, studies have demonstrated that pregnancy-associated complications such as pre-eclampsia or peri-partum infections are associated with increased VTE rates. In this review, we discuss the recent epidemiological studies, pathogenesis, risk factors and clinical presentation as well as therapeutic options for VTE during pregnancy and the postpartum period. We also provide proposed diagnostic algorithms for diagnosis and management of VTE during pregnancy and the postpartum period based on updated evidence. Finally, we highlight knowledge gaps to guide future research.

Management of anticoagulation in pregnant women with venous thromboembolism: An international survey of clinical practice

INTRODUCTION

Venous thromboembolism (VTE) is an important cause of maternal morbidity and mortality. During pregnancy, VTE is treated with low-molecular-weight-heparin (LMWH). Studies assessing the optimal duration and peripartum management of therapeutic anticoagulation are lacking. This survey aimed to assess clinician practices for the management of anticoagulation in pregnant women with acute VTE.

METHODS

An electronic survey consisting of clinical scenarios addressing anticoagulation management for VTE in pregnancy was created. The target sample was clinicians likely to be involved in the management of pregnant women with acute VTE. The survey completion rate and proportion of individuals selecting a response were determined.

RESULTS

96 respondents completed the survey including general internists (56.3%), hematologists (21.9%), and obstetricians (6.3%). In the management of a VTE in first or second trimester, most respondents preferred therapeutic LMWH until 6 weeks postpartum. In the first and second trimester, 48.0% and 37.5% of respondents, respectively, opted to reduce the dose of anticoagulation after 3 or 6 months. 29.2% of physicians opted for bridging with intravenous heparin around delivery when treating a VTE in the third trimester. 73.0% perceived an increased risk of clinically relevant non-major bleeding associated with the use of therapeutic anticoagulation in the peripartum and postpartum periods.

CONCLUSIONS

The survey highlights a wide variability of practice in the management of therapeutic anticoagulation in pregnancy. Larger scale studies with relevant clinical outcomes including thrombosis and bleeding risks are needed to inform clinical practice.

Prevention and management of venous thromboembolism in pregnancy: cutting through the practice variation

There is clinical practice variation in the area of prevention and management of venous thromboembolism (VTE) in pregnancy. There are limited data and differing recommendations across major clinical practice guidelines, especially relating to the role of postpartum low-molecular-weight heparin (LMWH) for patients with mild inherited thrombophilia and those with pregnancy-related VTE risk factors. This chapter explores the issues of practice variation and related data for postpartum VTE prevention. Controversial topics of VTE management in pregnancy are also reviewed and include LMWH dosing and the role of anti-Xa level monitoring, as well as peripartum anticoagulation management around labor and delivery.

Prophylaxis and management of venous thromboembolism during pregnancy and postpartum period

Introduction. Venous thromboembolism (VTE) is one of the lead causes for maternal mortality and morbidity during pregnancy in the majority of developed countries. The incidence rate of VTE per pregnancy-year increases during pregnancy and postpartum period about by 4-fold and at least 14-fold, respectively.

Aim: to analyze and summarize current view on risk factors of thrombotic events during gestation and to discuss recent guidelines for the management of venous thromboembolic complications during pregnancy and postpartum, by taking into account a balance between risks and benefits of using anticoagulants.

Materials and Methods. The literature search covering the last 10 years was carried out in the electronic scientific databases RSCI, PubMed/MEDLINE, and Embase. While formulating a search strategy for evidence-based information, the PICO method (P = Patient; I = Intervention; C = Comparison; O = Outcome) and the key terms “venous thromboembolism” and “pregnancy” were used.

Results. Risk factors were found to include a personal history of VTE, verified inherited or acquired thrombophilia, a family history of VTE and general medical conditions, such as immobilization, overweight, varicose veins, some hematological diseases and autoimmune disorders. VTE is considered being potentially preventable upon prophylactic administration of anticoagulants, but no high confidence randomized clinical trials comparing diverse strategies of thromboprophylaxis in pregnant women have been proposed so far. Because heparins do not cross the placenta, weight-adjusted therapeutic-dose low molecular weight heparins (LMWH) represent the anticoagulant treatment of choice for VTE during pregnancy. Once- and twice-daily dosing regimens are acceptable. However, no evidence suggesting benefits for measurement of factor Xa activities and consecutive LMWH dose adjustments to improve clinical outcomes are available. In case of uncomplicated pregnancy-related VTE, no routine administration of vitamin K antagonists, direct thrombin or factor Xa inhibitors, fondaparinux, or danaparoid is recommended. Lactating women may switch from applying LMWH to warfarin. Anticoagulation therapy should be continued for 6 weeks postpartum with total duration lasting at least for 3 months.

Conclusion. VTE is a challenging task in pregnant women expecting to apply a multi-faceted approach for its efficient solution by taking into account updated recommendations and personalized patient-oriented features.

Application of the RCOG Risk Assessment Model for Evaluating Postpartum Venous Thromboembolism in Chinese Women: A Case-Control Study

BACKGROUND Since China has not yet constructed its own risk assessment model (RAM) for pregnancy-related venous thromboembolism (VTE), more and more hospitals use the RCOG RAM for VTE risk prediction. However, the RCOG RAM was established based on Western populations, and its applicability in China is still uncertain. Thus, we aimed to evaluate the validity of the RCOG RAM in predicting postpartum VTE in Chinese maternity. MATERIAL AND METHODS This retrospective case-control study was conducted at the International Peace Maternity and Child Health Hospital (IPMCHH) from June 2016 to June 2020. The VTE group consisted of 38 women with postpartum VTE. For each VTE patient, 4 women without VTE who gave birth on the same day were randomly selected as the control group (n=152). The receiver operating characteristic (ROC) curve, calibration curve, and decision curve analysis (DCA) were used to evaluate the discrimination, accuracy, and validity of the RCOG RAM. Univariable analysis and multivariable logistic regression analysis were used to identify other related factors for postpartum VTE. RESULTS Compared with the low-risk group, the risk of VTE was 9.75-fold greater in the intermediate-risk group, and 90.00-fold greater in the high-risk group. The area under curve (AUC) of the model was 0.828 (95% CI: 0.762-0.894), with a score of 2 as its best cut-off value, which exactly matched the criterion recommended by the RCOG guidelines for pharmacological thromboprophylaxis. The calibration curves and DCA of the model also showed good accuracy. In addition to the factors included in the RCOG RAM, glucocorticoid therapy during pregnancy (adjusted OR=6.72, 95% CI: 1.56-28.91) and previous use of IUD (adjusted OR=7.11, 95% CI: 1.45-34.93) were associated with increased risk of postpartum VTE. CONCLUSIONS The RCOG RAM was found to be effective in predicting postpartum VTE, and has certain guiding significance for postpartum thromboprophylaxis in China.

Contemporary best practice in the management of pulmonary embolism during pregnancy

Approximately 1–2 per 1000 pregnancies are complicated by venous thromboembolism (VTE). VTE includes deep vein thrombosis (DVT) and pulmonary embolism (PE) and the diagnostic management of pregnancy-related VTE is challenging. Current guidelines vary greatly in their approach to diagnosing PE in pregnancy as they base their recommendations on scarce and weak evidence. The pregnancy-adapted YEARS diagnostic algorithm is well tolerated and is the most efficient diagnostic algorithm for pregnant women with suspected PE, with 39% of women not requiring computed tomographic pulmonary angiography. Low-molecular-weight heparin is the first-choice anticoagulant treatment in pregnancy and should be continued until 6 weeks postpartum and for a minimum of 3 months. Direct oral anticoagulants should be avoided in women who want to breastfeed. Management of delivery needs a multidisciplinary approach in order to decide on an optimal delivery plan. Neuraxial analgesia can be given in most patients, provided time windows since last low-molecular-weight heparin dose are respected. Women with a history of VTE are at risk of recurrence during pregnancy and in the postpartum period. Therefore, in most women with a history of VTE, thromboprophylaxis in subsequent pregnancies is indicated.

The reviews of this paper are available via the supplemental material section.

How I treat venous thromboembolism in pregnancy

One to 2 pregnant women in 1000 will experience venous thromboembolism (VTE) during pregnancy or postpartum. Pulmonary embolism (PE) is a leading cause of maternal mortality, and deep vein thrombosis leads to maternal morbidity, with postthrombotic syndrome potentially diminishing quality of life for a woman's lifetime. However, the evidence base for pregnancy-related VTE management remains weak. Evidence-based guideline recommendations are often extrapolated from nonpregnant women and thus weak or conditional, resulting in wide variation of practice. In women with suspected PE, the pregnancy-adapted YEARS algorithm is safe and efficient, rendering computed tomographic pulmonary angiography to rule out PE unnecessary in 39%. Low molecular weight heparin (LMWH) in therapeutic doses is the treatment of choice during pregnancy, and anticoagulation (LMWH or vitamin K antagonists [VKAs]) should be continued until 6 weeks after delivery, with a 3-month minimum total duration. LMWH or VKA use does not preclude breastfeeding. Postpartum, direct oral anticoagulants are an option if a woman does not breastfeed and long-term use is intended. Management of delivery, including type of analgesia, requires a multidisciplinary approach and depends on local preferences and patient-specific conditions. Several options are possible, including waiting for spontaneous delivery with temporary LMWH interruption. Prophylaxis for recurrent VTE prevention in subsequent pregnancies is indicated in most women with a history of VTE.

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.

Evaluation of therapeutic efficacy of anticoagulant drugs for patients with venous thromboembolism during pregnancy: A systematic review and meta-analysis

A meta-analysis based on published literature was undertaken to evaluate the efficacy of anticoagulant drugs for the treatment of venous thromboembolism during pregnancy. PubMed, Cochrane and Embase databases were searched from inception to September 2018 for relevant studies using indexed words, including qualified case-control and cohort studies. The meta-analysis used odds ratios (OR) and 95% confidence intervals (95% CI) to analyse the primary results. Nine studies were included in this meta-analysis, with a total of 834 cases and 3424 controls. There were no significant differences in the incidence of prenatal haemorrhage (OR 1.08, 95% CI 0.84-1.40), venous thromboembolism (OR 1.30, 95% CI 0.72-2.33) or caesarean section (OR 1.16, 95% CI 0.69-1.98) between the case group and the control group. The incidence of pulmonary embolism was significantly higher in the case group than in the control group (OR 3.90, 95% CI 1.23-12.34). However, there were a few limitations that may have influenced the results, so more randomized double-blind controlled studies of high quality are warranted to confirm the efficacy of anticoagulant therapy for venous thromboembolism in pregnancy.

Utilization of venous thromboembolism prophylaxis in American hospitalized pregnant women undergoing cesarean section

Background Pregnancy-related venous thromboembolism (VTE) is a leading preventable cause of maternal mortality in the United States; however, American guidelines for pharmacologic VTE prophylaxis remain less aggressive than other developed countries. The Safe Motherhood Initiative (SMI) combines aspects of American and international guidelines to increase utilization of prophylaxis and thereby decrease incidence of pregnancy-related VTE. Objectives To evaluate the prescribing and administration rates of pharmacologic VTE prophylaxis for women undergoing cesarean section (c-section) when retrospectively applying the SMI recommendations. Setting Large academic medical center in Sacramento, California, USA. Method This was a single-center retrospective cohort study of pregnant women undergoing c-section who would have met criteria for pharmacologic prophylaxis according to the SMI. Main outcome measures Prescribing and administration rates of mechanical and pharmacologic VTE prophylaxis. Secondary outcomes included incidence of thromboembolism within 6 weeks after c-section and thromboembolic associated mortality. Results A total of 616 charts were analyzed. When applying the SMI guidelines for VTE prophylaxis, the prescribing rates for mechanical and pharmacologic prophylaxis were 94.3% and 4.71% of patients, respectively, and 94.9% of ordered pharmacologic prophylaxis doses were administered. The incidence of 6-week post-partum VTE was 0.49%. There were no cases of VTE-associated mortality. Conclusion This study demonstrated that a large population of c-section patients fit the SMI criteria for pharmacologic VTE prophylaxis but did not receive it. We observed a 0.49% rate of VTE, which was slightly higher than the nationally reported average rate of 0.3%. With growing rates of pregnancy-associated VTE in the United States, perhaps a more aggressive guideline is warranted.

Low molecular weight heparin use during pregnancy and risk of postpartum hemorrhage: a systematic review and meta-analysis

INTRODUCTION

Postpartum hemorrhage (PPH) is the leading cause of maternal mortality worldwide with a prevalence rate of approximately 6%. Although most cases of PPH have no identifiable risk factors, the incidence of PPH has been associated to the thromboprophylaxis in pregnancy with low molecular weight heparin (LMWH). Thus, the aim of the study is to evaluate the risk of PPH in cases of pregnant women exposed to LMWH.

MATERIALS AND METHODS

Electronic research was performed in OVID, Scopus, ClinicalTrials.gov, MEDLINE, the PROSPERO International Prospective Register of Systematic Reviews, EMBASE, and the Cochrane Central Register of Controlled Trials through April 2016. We included randomized controlled trials, cohort and case-control studies of women who underwent thromboprophylaxis with LMWH during pregnancy compared to a control group (either placebo or no treatment). The primary outcome was the incidence of PPH. The summary measures were reported as relative risk (RR) or as mean differences (MD) with 95% confidence interval (CI).

RESULTS

Eight studies including 22,162 women were analyzed. Of the 22,162 women, 1320 (6%) were administered LMWH, 20,842 (94%) women formed the nonexposed group (control group). Women treated with LMWH had a higher risk of PPH (RR 1.45, 95%CI 1.02-2.05) compared to controls; there was no difference in mean of blood loss at delivery (MD -32.90, 95%CI 68.72-2.93) and in risk of blood transfusion at delivery (RR 1.24, 95%CI 0.62-2.51), respectively.

CONCLUSIONS

Women who receive LMWH during pregnancy have a significantly higher risk of developing PPH. Women who receive LMWH during pregnancy have neither significantly higher mean blood loss at delivery nor higher risk of blood transfusion.

Risk factors for severe postpartum hemorrhage: a case-control study

Background

In high-income countries, the incidence of severe postpartum hemorrhage (PPH) has increased. This has important public health relevance because severe PPH is a leading cause of major maternal morbidity. However, few studies have identified risk factors for severe PPH within a contemporary obstetric cohort.

Methods

We performed a case-control study to identify risk factors for severe PPH among a cohort of women who delivered at one of three hospitals in Norway between 2008 and 2011. A case (severe PPH) was classified by an estimated blood loss ≥1500 mL or the need for blood transfusion for excessive postpartum bleeding. Using logistic regression, we applied a pragmatic strategy to identify independent risk factors for severe PPH.

Results

Among a total of 43,105 deliveries occurring between 2008 and 2011, we identified 1064 cases and 2059 random controls. The frequency of severe PPH was 2.5% (95% confidence interval (CI): 2.32–2.62). The most common etiologies for severe PPH were uterine atony (60%) and placental complications (36%). The strongest risk factors were a history of severe PPH (adjusted OR (aOR) = 8.97, 95% CI: 5.25–15.33), anticoagulant medication (aOR = 4.79, 95% CI: 2.72–8.41), anemia at booking (aOR = 4.27, 95% CI: 2.79–6.54), severe pre-eclampsia or HELLP syndrome (aOR = 3.03, 95% CI: 1.74–5.27), uterine fibromas (aOR = 2.71, 95% CI: 1.69–4.35), multiple pregnancy (aOR = 2.11, 95% CI: 1.39–3.22) and assisted reproductive technologies (aOR = 1.88, 95% CI: 1.33–2.65).

Conclusions

Based on our findings, women with a history of severe PPH are at highest risk of severe PPH. As well as other established clinical risk factors for PPH, a history of severe PPH should be included as a risk factor in the development and validation of prediction models for PPH.

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.

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.

Anticoagulant therapy for venous thromboembolism during pregnancy: a systematic review and a meta-analysis of the literature

Venous thromboembolism (VTE) is one of the most relevant causes of maternal death in industrialized countries. Low molecular weight heparin (LMWH), continued throughout the entire pregnancy and puerperium, is currently the preferred treatment for patients with acute VTE occurring during pregnancy. However, information on the efficacy and safety of anticoagulant drugs in this setting is extremely limited. We carried out a systematic review and a meta-analysis of the literature to provide an estimate of the risk of bleeding complications and VTE recurrence in patients with acute VTE during pregnancy treated with antithrombotic therapy. The weight mean incidence (WMI) of bleeding and thromboembolic events and the corresponding 95% confidence interval (CI) were calculated. Eighteen studies, giving a total of 981 pregnant patients with acute VTE, were included. LMWH was prescribed to 822 patients; the remainder were treated with unfractionated heparin. Anticoagulant therapy was associated with WMIs of major bleeding of 1.41% (95% CI 0.60-2.41%; I) antenatally and 1.90% (95% CI 0.80-3.60%) during the first 24 h after delivery. The estimated WMI of recurrent VTE during pregnancy was 1.97% (95% CI 0.88-3.49%; I(2) 39.5%). Anticoagulant therapy appears to be safe and effective for the treatment of pregnancy-related VTE, but the optimal dosing regimens remain uncertain.

How I treat pregnancy-related venous thromboembolism

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