When should Unfractionated Heparin (UFH) be stopped prior to delivery in a pregnant woman with a mechanical Mitral Valve Replacement (MVR) on Low Molecular Weight Heparin (LMWH)?

Timing of Unfractionated Heparin Discontinuation Prior to Delivery in Pregnant Women with Mechanical MVR

Unfractionated heparin (UFH) should be stopped at least 6 hours before planned vaginal delivery in pregnant women with mechanical mitral valve replacement who are transitioning from LMWH to UFH before delivery. 1

Anticoagulation Management Timeline for Delivery

For pregnant women with mechanical mitral valve replacement who are on LMWH during pregnancy, the following timeline should be followed:

1. At least 1 week before planned delivery:

   • Switch from LMWH to intravenous UFH (with an aPTT target of 2 times control) 1

2. At least 36 hours before planned delivery:

   • If still on LMWH, switch to continuous intravenous UFH (with an aPTT target of 2 times control) 1

3. At least 6 hours before planned vaginal delivery:

   • Stop UFH completely to reduce the risk of maternal bleeding and allow safe placement of epidural anesthesia 1

4. Coordination with teams:

   • The exact timing should be coordinated with obstetrics and anesthesia teams 1

Rationale and Considerations

Risk Management

• Although LMWH does not cross the placenta, the risk of maternal hemorrhage is high if delivery occurs while the mother is on LMWH 1
• The 6-hour window before delivery is critical to reduce the risk of maternal bleeding and allow safe placement of epidural anesthesia 1

Special Circumstances

• For emergency or unplanned delivery: If labor begins or urgent delivery is required while the patient is on warfarin, cesarean section should be performed after reversal of anticoagulation 1
• For cesarean section: The same timing principles apply, with UFH discontinuation at least 6 hours before the procedure

Potential Complications and Monitoring

• Maternal hemorrhage: The primary concern when discontinuing anticoagulation too close to delivery
• Valve thrombosis: A risk when anticoagulation is subtherapeutic for extended periods
• Epidural hematoma: A rare but serious complication if epidural anesthesia is placed while the patient is anticoagulated

Evidence Quality

The recommendations are based on Class 1, Level C-LD evidence from the 2020 AHA/ACC guidelines, indicating that while the recommendation is strong, it is derived from limited data 1. The 6-hour window before delivery has become standard practice despite limited high-quality studies specifically addressing this timing.

Common Pitfalls to Avoid

• Inadequate transition time: Failing to switch from LMWH to UFH at least 36 hours before delivery
• Stopping anticoagulation too late: Not allowing the full 6-hour window before delivery, increasing bleeding risk
• Lack of team coordination: Not involving obstetrics and anesthesia teams in planning the anticoagulation cessation timeline
• Resuming anticoagulation too early: Postpartum anticoagulation should be resumed carefully to balance thrombotic and hemorrhagic risks

Following these guidelines will help optimize outcomes for both mother and baby by balancing the risks of thromboembolism against the risks of peripartum hemorrhage.