How can we best treat and monitor VTE during pregnancy?
Unfractionated heparin and low-molecular-weight heparin are equally effective for the treatment of acute venous thromboembolism (VTE) in pregnancy (strength of recommendation [SOR]: C; based on expert opinion and 1 low-power cohort study). Low- molecular-weight heparin may be associated with fewer bleeding events than unfractionated heparin (SOR: B; extrapolated from a randomized controlled trial of thromboprophylaxis in pregnancy). Unfractionated heparin for treatment of VTE should be given by IV bolus followed by continuous infusion, maintaining the activated partial thromboplastin time (aPTT) in therapeutic range for at least 5 days, followed by subcutaneous heparin 2 or 3 times daily to maintain aPTT levels 1.5 to 2.5 times normal for at least 3 months (SOR: C, expert opinion). Low-molecular-weight heparin should be initially dosed based on weight as for nonpregnant patients, then adjusted to goal peak antifactor Xa levels of 0.5-1.2 IU/mL (SOR: C; expert opinion). The US Food and Drug Administration has labeled warfarin as category X, indicating that it is contraindicated during pregnancy due to fetal loss and probable teratogenicity.
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