What is the risk of bleeding with anticoagulants (anticoagulant medications), such as warfarin (Warfarin), during pregnancy?

From the Guidelines

Warfarin use during pregnancy poses a significant risk of bleeding complications, including fetal intracranial hemorrhage, and should be avoided if possible, especially considering the potential for miscarriage, spontaneous abortion, warfarin embryopathy, or fetal death 1. The risk of bleeding with anticoagulants, such as warfarin, during pregnancy is a critical concern due to the potential for serious maternal and fetal complications. Key considerations include:

• The maternal mortality rate remains high, over 1%, for women with mechanical heart valves, emphasizing the need for careful anticoagulation management 1.
• Warfarin, although effective at preventing thrombotic complications, crosses the placenta and can cause severe fetal complications, making its use during pregnancy challenging 1.
• Alternative anticoagulation strategies, such as the use of low molecular weight heparin (LMWH) or unfractionated heparin, may be preferred due to their lower risk of fetal complications, but each has its own set of challenges and requirements for monitoring and dosing adjustments. The management of anticoagulation during pregnancy, especially for women with mechanical heart valves, requires a tailored approach, considering the trade-offs between maternal safety and fetal safety. Important factors to consider include:
• The choice of anticoagulant: Warfarin, LMWH, or unfractionated heparin, each with its benefits and risks.
• The timing and dosing of anticoagulants, which may need to be adjusted throughout pregnancy due to physiological changes.
• The need for regular monitoring of anticoagulant levels to minimize the risk of bleeding complications.
• Coordination of anticoagulant management with other aspects of care, such as regional anesthesia timing during delivery.

From the FDA Drug Label

Anticoagulation is contraindicated in any localized or general physical condition or personal circumstance in which the hazard of hemorrhage might be greater than the potential clinical benefits of anticoagulation, such as: Pregnancy Warfarin sodium tablets are contraindicated in women who are or may become pregnant because the drug passes through the placental barrier and may cause fatal hemorrhage to the fetus in utero.

The risk of bleeding with anticoagulants, such as warfarin, during pregnancy is high. Warfarin may cause fatal hemorrhage to the fetus in utero 2.

From the Research

Risk of Bleeding with Anticoagulants during Pregnancy

• The risk of bleeding with anticoagulants, such as warfarin, during pregnancy is a concern due to the potential for maternal and fetal complications 3, 4, 5, 6, 7.
• Low-molecular-weight heparin (LMWH) is commonly recommended as an anticoagulant during pregnancy, with a reported risk of antepartum bleeding of 0.5% and postpartum hemorrhage of 1% with prophylactic dosing, and 1.5% and 2% respectively with treatment dosing 3.
• Enoxaparin, a type of LMWH, has been shown to be safe for the fetus and has a low risk of maternal side effects, including increased bleeding in 2% of cases 5.
• A retrospective study of 744 pregnancies in women with rheumatic heart disease and valve replacement found that LMWH was effective in preventing major thromboembolic complications, with a low risk of hemorrhagic complications 4.
• Another study found that LMWH can be used in pregnancy for various indications, including valvular heart disease, atrial fibrillation, and thrombophilia, with a low risk of thromboembolic events and no documented thrombocytopenia or clinical fracture 6.
• However, the use of warfarin during pregnancy is associated with a higher risk of thrombotic events, and guidelines recommend switching to alternative therapy during the first trimester due to the teratogenic effects of vitamin K antagonists 7.