Anticoagulation During Pregnancy: Evolving Strategies

Alshawabkeh L, Economy KE, Valente AM.
Anticoagulation During Pregnancy: Evolving Strategies With a Focus on Mechanical Valves. J Am Coll Cardiol 2016;68:1804-1813.

The following are nine key points to remember from this review article on the use of anticoagulant medications during pregnancy:

  1. Pregnancy is a known hypercoagulable state. For example, there is a five-fold increased risk of venous thromboembolism (VTE) during pregnancy that persists for 12 weeks postpartum. This occurs due to increased levels of factors VII, VIII, X, von Willebrand factor, and fibrinogen along with decreased protein S.
  2. Choosing anticoagulant therapies during pregnancy involves a balance of risks and benefits to both the mother and fetus.
  3. Delivery is the highest period of bleeding for a pregnant woman, including the placement of regional anesthesia and Cesarean delivery. Low molecular weight heparin (LMWH) is recommended to be discontinued 12-24 hours prior to lumbar instrumentation, along with an international normalized ratio (INR) ≤1.5.
  4. Vitamin K antagonists (e.g., warfarin) cross the placenta and have a dose-dependent relationship with adverse outcomes (e.g., miscarriage, stillbirth, embryopathy). These usually occur with doses >5 mg/day.
  5. Women with mechanical heart valves are at high risk of thromboembolic complications. These patients can either be treated with continued warfarin therapy (especially if daily dose is ≤5 mg and INR ≤5) or use of weight-based LMWH dosed twice daily. Use of direct oral anticoagulants (e.g., dabigatran) should NOT be used given their risk of mechanical valve thrombosis.
  6. Women with a history of thrombophilia or VTE on chronic anticoagulation should continue anticoagulation during (and after) pregnancy. Weight-based LMWH is the preferred agent, but warfarin (daily dose ≤5) is an alternative. Use of direct oral anticoagulants (e.g., rivaroxaban) has not been systematically studied, but they do cross the placenta and their safety cannot be substantiated.
  7. Women with a history of thrombophilia, but no personal VTE history should receive surveillance or prophylactic doses of LMWH antepartum, but strongly consider full therapeutic doses postpartum. Women with a personal history of VTE on chronic anticoagulation should receive therapeutic doses of LMWH antepartum and postpartum.
  8. Weight-based LMWH should be accompanied by peak anti-Xa levels drawn 4-6 hours post-dose to achieve a goal level of 1.0-1.2 U/ml.
  9. Warfarin is listed as pregnancy category D, does cross the placenta, but is not found in breast milk. LMWH is listed as pregnancy category B, does not cross the placenta, and is not found in breast milk.

Keywords: Anticoagulants, Antithrombins, Anesthesia, Factor VII, Fetal Diseases, Fibrinogen, Fibrinolytic Agents, Heart Valve Diseases, Heparin, Low-Molecular-Weight, Postpartum Period, Pregnancy, Protein S, Risk Assessment, Secondary Prevention, Stillbirth, Thrombophilia, Thrombosis, Venous Thromboembolism, Vitamin K, Warfarin, von Willebrand Factor

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