Bemiparin versus enoxaparin as thromboprophylaxis following vaginal and abdominal deliveries: a prospective clinical trial

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.

Preventing Postpartum Venous Thromboembolism in 2022: A Narrative Review

The postpartum period represents the most critical time for pregnancy-associated venous thromboembolism (VTE), which is responsible for substantial morbidity and an important cause of maternal mortality. The estimated risk of postpartum VTE of about 1/1,000 deliveries can be modulated with the knowledge of maternal and obstetrical risk factors, although a precise estimate remains challenging in individuals. The use of postpartum low-dose low-molecular-weight heparins are tailored at intermediate and high-risk groups to reduce the thrombotic burden, despite the lack of dedicated randomized controlled trials. In this review, we will highlight the contemporary evidence on the risk of postpartum VTE, its stratification and its prevention. We will also discuss our knowledge on the values and preferences of women for postpartum thromboprophylaxis and their adherence to treatment.

Venous thromboembolism prophylaxis for women at risk during pregnancy and the early postnatal period

BACKGROUND

Venous thromboembolism (VTE), although rare, is a major cause of maternal mortality and morbidity. Some women are at increased risk of VTE during pregnancy and the early postnatal period (e.g. caesarean section, family history of VTE, or thrombophilia), and so prophylaxis may be considered. As some methods of prophylaxis carry risks of adverse effects, and risk of VTE is often low, benefits of thromboprophylaxis may be outweighed by harms.

OBJECTIVES

To assess the effects of thromboprophylaxis during pregnancy and the early postnatal period on the risk of venous thromboembolic disease and adverse effects in women at increased risk of VTE.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (18 October 2019). In addition, we searched ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) for unpublished, planned and ongoing trial reports (18 October 2019).

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

At least two review authors assessed trial eligibility, extracted data, assessed risk of bias, and judged certainty of evidence for selected critical outcomes (using GRADE). We conducted fixed-effect meta-analysis and reported data (all dichotomous) as summary risk ratios (RRs) with 95% confidence intervals (CIs).

MAIN RESULTS

Twenty-nine trials (involving 3839 women), overall at moderate to high risk of bias were included. Trials were conducted across the antenatal, peripartum and postnatal periods, with most in high-income countries. Interventions included types and regimens of heparin (low molecular weight heparin (LMWH) and unfractionated heparin (UFH)), hydroxyethyl starch (HES), and compression stockings or devices. Data were limited due to a small number of trials in comparisons and/or few or no events reported. All critical outcomes (assessed for comparisons of heparin versus no treatment/placebo, and LMWH versus UFH) were considered to have very low-certainty evidence, downgraded mainly for study limitations and imprecise effect estimates.  Maternal death was not reported in most studies. Antenatal (± postnatal) prophylaxis For the primary outcomes symptomatic thromboembolic events pulmonary embolism (PE) and/or deep vein thrombosis (DVT), and the critical outcome of adverse effects sufficient to stop treatment, the evidence was very uncertain.  Symptomatic thromboembolic events: - heparin versus no treatment/placebo (RR 0.39; 95% CI 0.08 to 1.98; 4 trials, 476 women; very low-certainty evidence); - LMWH versus UFH (RR 0.47; 95% CI 0.09 to 2.49; 4 trials, 404 women; very low-certainty evidence); Symptomatic PE: - heparin versus no treatment/placebo (RR 0.33; 95% CI 0.02 to 7.14; 3 trials, 187 women; very low-certainty evidence); - LMWH versus UFH (no events; 3 trials, 287 women); Symptomatic DVT: - heparin versus no treatment/placebo (RR 0.33; 95% CI 0.04 to 3.10; 4 trials, 227 women; very low-certainty evidence); - LMWH versus UFH (no events; 3 trials, 287 women); Adverse effects sufficient to stop treatment: - heparin versus no treatment/placebo (RR 0.49; 95% CI 0.05 to 5.31; 1 trial, 139 women; very low-certainty evidence); - LMWH versus UFH (RR 0.07; 95% CI 0.01 to 0.54; 2 trials, 226 women; very low-certainty evidence). Peripartum/postnatal prophylaxis Vaginal or caesarean birth When UFH and no treatment were compared, the effects on symptomatic thromboembolic events (RR 0.16; 95% CI 0.02 to 1.36; 1 trial, 210 women; very low-certainty evidence), symptomatic PE (RR 0.16; 95% CI 0.01 to 3.34; 1 trial, 210 women; very low-certainty evidence), and symptomatic DVT  (RR 0.27; 95% CI 0.03 to 2.55; 1 trial, 210 women; very low-certainty evidence) were very uncertain.  Maternal death and adverse effects sufficient to stop treatment were not reported. Caesarean birth Symptomatic thromboembolic events: - heparin versus no treatment/placebo (RR 1.30; 95% CI 0.39 to 4.27; 4 trials, 840 women; very low-certainty evidence); - LMWH versus UFH (RR 0.33; 95% CI 0.01 to 7.99; 3 trials, 217 women; very low-certainty evidence); Symptomatic PE: - heparin versus no treatment/placebo (RR 1.10; 95% CI 0.25 to 4.87; 4 trials, 840 women; very low-certainty evidence); - LMWH versus UFH (no events; 3 trials, 217 women);  Symptomatic DVT: - heparin versus no treatment/placebo (RR 1.30; 95% CI 0.24 to 6.94; 5 trials, 1140 women; very low-certainty evidence); LMWH versus UFH (RR 0.33; 95% CI 0.01 to 7.99; 3 trials, 217 women; very low-certainty evidence); Maternal death: - heparin versus placebo (no events, 1 trial, 300 women); Adverse effects sufficient to stop treatment: - heparin versus placebo (no events;  1 trial, 140 women). Postnatal prophylaxis No events were reported for LMWH versus no treatment/placebo for: symptomatic thromboembolic events, symptomatic PE and symptomatic DVT (all 2 trials, 58 women), or maternal death (1 trial, 24 women). Adverse effects sufficient to stop treatment were not reported. We were unable to conduct subgroup analyses due to lack of data. Sensitivity analysis including the nine studies at low risk of bias did not impact overall findings.

AUTHORS' CONCLUSIONS

The evidence is very uncertain about benefits and harms of VTE thromboprophylaxis in women during pregnancy and the early postnatal period at increased risk of VTE. Further high-quality very large-scale randomised trials are needed to determine effects of currently used treatments in women with different VTE risk factors. As sufficiently large definitive trials are unlikely to be funded, secondary data analyses based on high-quality registry data are important.

Estimating the risk thresholds used by guidelines to recommend postpartum thromboprophylaxis

BACKGROUND

Guidelines for postpartum thromboprophylaxis are mostly expert based. Acceptable postpartum venous thromboembolism (VTE) risk thresholds to justify the use of thromboprophylaxis are ill defined.

OBJECTIVE

To compare the proportion of postpartum women with recommended thromboprophylaxis according to the Royal College of Obstetricians and Gynecologists (RCOG), American College of Obstetricians and Gynecologists (ACOG), and American College of Chest Physicians (ACCP) guidelines, and to estimate their threshold of risk of VTE.

METHODS

We collected maternal, obstetrical, and fetal characteristics among all women who delivered at the Geneva University Hospitals in January 2019 through medical chart review. We determined for each woman the recommended strategy of thromboprophylaxis according to each guideline. We indirectly estimated individual absolute VTE risks using a validated risk prediction model (Sultan).

RESULTS

Among 344 women (mean age 32.2 years), with 23.3% of cesarean deliveries (CD), the RCOG guideline categorized 40.1% of all deliveries, 25.4% of vaginal deliveries (VD), and 88.8% of CD as requiring thromboprophylaxis. The ACOG and ACCP guidelines, which focus on CD, categorized fewer women as high risk (35.0% and 40.0% of CD, respectively). The mean estimated risk of VTE was 0.07% in all participants, 0.12% in those with recommended thromboprophylaxis according to the RCOG, and 0.20% among women after CD with recommended thromboprophylaxis by the ACOG and ACCP guidelines.

CONCLUSIONS

Our data highlight important variations in the proportion of thromboprophylaxis recommendation between guidelines. Risk thresholds to recommend the use of heparin appear very low, and may correlate with a high, and perhaps undesirable, number needed to treat to prevent VTE events.

Postpartum thromboprophylaxis in a multireligious cohort: a retrospective review of indications and uptake

Strategies to prevent mortality from obstetric venous thromboembolism begin with identification, risk stratification and subsequently, implementation of prophylactic measures. We sought to identify the burden of pharmacologic thromboprophylaxis in postpartum women, including the main clinical indications and its uptake in a multireligious population, with Islam as the official religion. A total of 2514 deliveries between 1st January to 31st December 2016, across three centres in Malaysia were reviewed retrospectively from hospital-based registries. 770 (30.62%) patients fulfilled the criteria for thromboprophylaxis based on the revised 2015 criteria proposed by the Royal College of Obstetricians and Gynaecologists. A combination of age, parity, BMI, caesarean section and preterm births were the main indications. One out of the five patients who delivered vaginally required thromboprophylaxis. In our setting with a sizable Muslim population, low molecular weight heparin was the thromboprophylaxis of choice in more than two-third of the patients. The information obtained from this study allows better local resource planning. Impact statement What is already known on this subject: Risk factors for venous thromboembolism in pregnancy and puerperium are largely drawn from registries due to the rarity of the index event. Up to 7% of women require antenatal thromboprophylaxis based on the criteria proposed by the Royal College of Obstetrician and Gynaecologists in 2009. What do the results of this study add: Using the RCOG guideline revised in 2015, a significant proportion of women delivering vaginally would require postnatal thromboprophylaxis based on age, parity and BMI. When either age or parity, both with relatively low odds ratio for thrombosis were omitted, a substantial proportion of women would not achieve the threshold for prophylaxis. Despite a sizable Muslim population in the country, the uptake of low molecular weight heparin was relatively high. What are the implications of these findings for clinical practice and/or future research: Cost-benefit studies should consider the adjusted odds ratio of individual indications on a VTE event. While uptake and acceptability is high, prospective studies on medication adherence is equally pertinent.

Bemiparin versus Enoxaparin in the Prevention of Venous Thromboembolism among Intensive Care Unit Patients

Background:

Critically ill patients are considered a high-risk group for developing venous thromboembolism (VTE). Due to their impaired cardiopulmonary reserve, these VTEs may result in significant morbidity and mortality. In this study, we compared two types of low molecular weight heparin, enoxaparin, and bemiparin, as regards to their efficacy and safety in VTE prevention among Intensive Care Unit (ICU) patients.

Methods:

This study was a prospective, randomized trial of 100 critically ill patients who are at high risk for developing VTE were included in this study and assigned to receive subcutaneous injections of either 3500 international units (IU) anti-factor Xa of bemiparin sodium or 40 mg of enoxaparin given once a day and patient were followed for 60 days after initiation of anticoagulant therapy for the development of documented deep venous thrombosis (DVT) using bilateral lower limb venous duplex, documented pulmonary embolism using computed tomography pulmonary angiography, and complications related to injectant anticoagulant.

Results:

Confirmed DVT was observed in two patients (4%) in the bemiparin group compared with 10 patients (20%) in the enoxaparin group with P < 0.05. Confirmed pulmonary embolism (PE) was observed in seven patients (14%) in the enoxaparin group with no recorded cases of confirmed PE in the bemiparin group (P < 0.05). No deaths were recorded in either group. Adverse events such as ecchymosis or hematoma at the injection site were observed in one patient (2%) in the bemiparin group and eight patients (16%) in the enoxaparin group (P < 0.05). There was no significant statistical difference between both groups as regards other adverse effects and complications related to the injectant anticoagulant.

Conclusion:

Bemiparin was superior to enoxaparin as a prophylactic anticoagulant for VTE in critically ill patients with less adverse local complications at the injection site. The study was registered on www.clinicaltrials.gov. Registration ID: NCT02795065. Registered June 8, 2016.