Increased Heparin Dose to Prevent VTE in Pregnant Women

According to a study published in Lancet, the optimal dose of low-molecular-weight heparin for venous thromboembolism (VTE) prevention in pregnant and post-partum women with a history of (VTE) has not been established.

Researchers compared weight-adjusted intermediate-dose and fixed low-dose low-molecular-weight heparin and found the intermediate dose during the antepartum and post-partum periods did not appear to reduce risk of recurrence when compared with the fixed low-dose.

Between April 24, 2013 to October 31, 2020, this randomized trial, named “Highlow”, enrolled 1110 pregnant women aged 18 years or older with a history of confirmed VTE and a gestational age of 14 weeks or less. The cohort was split evenly between weight-adjusted intermediate- and fixed low-dose low-molecular-weight heparin groups.

Increased Heparin Dose Doesn’t Appear to Reduce VTE

The primary efficacy end point was objectively confirmed VTE events including deep vein thrombosis (DVT), pulmonary embolism (PE), and unusual site venous thrombosis, as assessed by an independent committee among the intention to treat population. THe primary safety end point was major bleeding throughout the antepartum, early post-partum, and late post-partum periods.

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Overall, VTE events occured in 11 (2%) of 555 women in the weight-adjusted intermediate-dose group compared with 16 (3%0 of 555 in the fixed low-dose group (relative risk [RR], 0.69; 95% CI, 0.32-1.47; P=.33), the authors reported. In the antepartum period, 5 (1%) women in both the intermediate-dose and low-dose groups experienced VTE. In the post-partum period, VTE occurred in 6 (1%) and 11 (2%) in the intermediate- and low-dose groups, respectively.

Finally, in the safety analysis population (n=1045), major bleeding events during treatment occurred in 23 (4%) of 520 women in the intermediate-dose group and 20 (4%) of 525 women in the low-dose group (RR, 1.16; 95% CI, 0.65-2.09).

Ultimately, the authors suggested “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.”

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