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Chapter 184. Anticoagulation during Pregnancy

Imre Rédai, MD, FRCA

Long-term therapeutic anticoagulation during pregnancy is necessary for:

  • History of venous thromboembolism in prior pregnancy
  • History of recurrent thromboembolism
  • Thrombophilias
  • Mechanical heart valve prosthesis
  • Certain medical conditions (Eisenmenger, severe heart failure, chronic atrial fibrillation)

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Antithrombotic Agents in Pregnancy
MedicationCharacteristicsComments
Unfractionated heparin (UFH)
  • Does not cross placenta
  • Bone demineralization with long-term use
  • Risk of HIT
  • Does not cross into breast milk in significant amounts (safe with breast-feeding)
  • Reversal of anticoagulation for delivery seldom necessary
  • If reversal is needed (usually for Cesarean delivery), titrate protamine
Low-molecular-weight heparin (LMWH)
  • Does not cross placenta
  • Bone demineralization may occur with long-term use
  • Does not cross into breast milk in significant amounts (safe with breast-feeding)
  • Should be converted to UFH at 36 weeks gestation
  • In an emergency situation reversal is not complete (discuss with hematologist dose of protamine)
  • Substitution of LMWH for warfarin in patients with mechanical heart valves remains controversial
Warfarin
  • Freely crosses placental barrier
  • Fetal effects appear to be dose related rather than INR related
  • Fetal hemorrhage may occur
  • Neonatal hemorrhage may occur (if patient has not been converted to UFH, delivery should be via Cesarean section)
  • Does not cross into breast milk in significant amounts (safe with breast-feeding)
  • Use is limited to patients with mechanical heart valves
  • Should not be used between 6 and 13 weeks of gestation to minimize teratogenic effects
  • Dose should be kept under 5 mg daily
  • Switch to UFH at 36 weeks
  • If emergency delivery is necessary, both mother and newborn should receive FFP to reverse drug effects (vitamin K onset is too slow in this clinical setting)

Anticoagulation should be restarted 6 hours following vaginal delivery and 12 hours following Cesarean delivery if there are no clinical signs of ongoing hemorrhage.

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Anesthesia Considerations in the Anticoagulated Parturient
Labor analgesia
  • Neuraxial analgesia should not be attempted in an actively anticoagulated patient
  • Follow neurological status throughout labor and postpartum for spinal hematoma
  • Neuraxial analgesia in patients on prophylactic UFH is safe
  • UFH in intermediate and therapeutic dose should be stopped for 6 h and a normal aPTT documented before neuraxial analgesia is attempted
  • Check platelet count if patient has received UFH for at least 4 days
  • Prophylactic LMWH should be stopped for at least 12 h
  • Intermediate and therapeutic LMWH should be stopped for at least 24 h
  • Warfarin should be stopped for at least 5 days and a normal PT/INR should be documented; furthermore, time should be allowed for substitute antithrombotic agents to wear off (bleeding risk increases in patients recently converted from warfarin to UFH or LMWH)
Vaginal deliveryRisk of bleeding in mother may be increased
  • Evaluate patient thoroughly for potential intrapartum and postpartum hemorrhage
  • Establish adequate venous access
  • Consider reversing heparin effects with protamine
  • Have 4 U PRBC cross-matched
  • Evaluate and review airway throughout labor
Cesarean section
  • Neuraxial anesthesia should not be attempted in ...

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