Low-dose low-molecular weight heparin comparable to intermediate-dose for risk of venous thromboembolism in peripartum women

1. Risk of venous thromboembolism in the antepartum and postpartum period was comparable between the intermediate- and low-dose low-molecular weight heparin groups.

2. There was no difference in major bleeding between low-dose and intermediate-dose heparin.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Venous thromboembolism (VTE) is a common occurrence in pregnancy, leading to increased risk of maternal morbidity and mortality. Current guidelines suggest low-molecular-weight heparin (LMWH) for post-partum thromboprophylaxis; however, the optimal dose of LMWH remains unclear. This randomized trial aimed to compare intermediate-dose versus low-dose LMWH for prevention of recurrent VTE in pregnancy and post-partum period in patients with a previous history of VTEs. Patients were randomly assigned to either group and given once daily subcutaneous injections until 6 weeks post-partum. The primary efficacy outcome was incidence of VTE while the primary safety outcome included risk of major antepartum and postpartum bleeding. According to study results, there was no significant difference between intermediate-dose and low-dose heparin for pregnancy-related recurrent VTE and major bleeding events. This study was strengthened by a large sample size with patients from multiple countries, adding to its validity.

Click to read the study in The Lancet

Relevant Reading: Pregnancy-Adapted YEARS Algorithm for Diagnosis of Suspected Pulmonary Embolism

In-depth [randomized-controlled trial]: Between April 24, 2013, and October 31, 2020, 1339 pregnant women were screened for eligibility from 70 hospitals in 9 countries. Included were women ≥ 18 years old who were ≤ 14 weeks pregnant with a known history of VTEs. Altogether, 1110 patients (555 to intermediate-dose and 555 to fixed low-dose) were included in the final analysis. The primary efficacy outcome of VTE was comparable in the intermediate (2%, 11 of 555) and fixed low-dose (3%, 16 of 555) groups (relative risk [RR] 0.69, 95% confidence interval [CI] 0.32-1.47, p=0.33). This was also the case for incidence of VTE in antepartum (1% for intermediate-dose and low-dose groups) and postpartum (1% for intermediate-dose and 2% for low-dose group) women. Furthermore, the primary safety outcome of major bleeding was comparable between groups (4% each, RR 1.16, 95% CI 0.65-2.09). Findings from this study suggest that intermediate-dose LMWH does not decrease the risk of VTE compared to low-dose heparin in pregnant women.

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