In a pregnant woman with peripartum cardiomyopathy and an ejection fraction below 35% or a documented left‑ventricular thrombus, how long should therapeutic low‑molecular‑weight heparin be continued?

Duration of LMWH in Peripartum Cardiomyopathy with Severe LV Dysfunction or Thrombus

In pregnant women with peripartum cardiomyopathy and ejection fraction below 35% or documented left ventricular thrombus, therapeutic-dose LMWH should be continued for at least 6 weeks postpartum (minimum total duration of 3 months from diagnosis), with consideration for extended anticoagulation until cardiac function recovers or indefinitely if thrombus persists or EF remains severely reduced. 1

Antepartum Management

Initiation and Dosing

• Start therapeutic-dose LMWH immediately upon diagnosis of peripartum cardiomyopathy with EF <35% or documented LV thrombus, as these patients face substantially elevated thromboembolic risk 2, 3
• Use weight-adjusted therapeutic dosing: enoxaparin 1 mg/kg twice daily or dalteparin 100 IU/kg twice daily 1
• Target anti-Xa levels of 0.6-1.2 IU/mL measured 4-6 hours post-dose 1

Monitoring Requirements

• Check anti-Xa levels weekly as pregnancy progresses, since volume of distribution changes and dose adjustments are frequently needed 1
• Perform monthly echocardiography to assess for thrombus resolution and ventricular function recovery 1
• Monitor platelet counts to detect heparin-induced thrombocytopenia, though risk is markedly lower with LMWH than unfractionated heparin 1

Peripartum Transition

Timing of LMWH Discontinuation

• Stop LMWH at least 24 hours before planned induction of labor or cesarean section to allow adequate clearance and enable neuraxial anesthesia if desired 1
• For spontaneous labor, discontinue LMWH when labor begins or membranes rupture 1
• This 24-hour window reduces bleeding risk while minimizing the period without anticoagulation 1

Delivery Considerations

• If delivery occurs while still on therapeutic anticoagulation, cesarean delivery is indicated to minimize hemorrhagic complications 1
• Epidural analgesia cannot be used unless LMWH has been discontinued at least 12 hours before epidural placement 1

Postpartum Management

Resumption and Duration

• Resume therapeutic-dose LMWH 12-24 hours after delivery if no bleeding complications occur 1
• Continue anticoagulation for at least 6 weeks postpartum, ensuring minimum total treatment duration of 3 months from initial diagnosis 1
• This recommendation parallels guidance for acute VTE in pregnancy, where the thrombotic risk extends well into the postpartum period 1

Transition to Oral Anticoagulation

• After the immediate postpartum period (typically after hospital discharge), transition to warfarin with INR target 2.0-3.0 may be considered for ease of long-term management 1, 4
• Warfarin is compatible with breastfeeding 5, 4
• Maintain therapeutic anticoagulation during the transition period with LMWH overlap until INR is therapeutic for 2 consecutive days 1

Extended Anticoagulation Considerations

• Continue anticoagulation beyond 6 weeks postpartum if:
  • LV thrombus persists on follow-up echocardiography 6, 2
  • EF remains <30-35% despite medical therapy 2, 7
  • Patient develops atrial fibrillation 1
• The high rate of thromboembolic events in peripartum cardiomyopathy (particularly with EF <30%) supports aggressive anticoagulation strategies 2, 3, 7

Critical Pitfalls to Avoid

Inadequate Dosing

• Do not use prophylactic-dose LMWH in patients with documented thrombus or severely reduced EF—therapeutic dosing is required 2
• Subtherapeutic anticoagulation has been implicated in valve thrombosis cases in pregnant women with mechanical valves, and similar risks apply to LV thrombi 1

Premature Discontinuation

• The postpartum period carries the highest thrombotic risk, with most thromboembolic events occurring in the first 6 weeks after delivery 1, 5
• Do not stop anticoagulation at hospital discharge—ensure clear plans for 6-week minimum postpartum treatment 1

Monitoring Failures

• Failure to adjust LMWH dosing as pregnancy progresses can lead to subtherapeutic levels and treatment failure 1
• Weekly anti-Xa monitoring is essential, not optional, during pregnancy 1

Special Circumstances

If Thrombus Becomes Mobile

• Mobile thrombi represent extremely high embolic risk 6
• Consider switching to intravenous unfractionated heparin for more precise control and shorter half-life 6
• Surgical thrombectomy may be necessary if medical management fails 6

Recovery of Cardiac Function

• Even if EF improves to >45%, complete the minimum 3-month anticoagulation course 1
• Peripartum cardiomyopathy has high recovery rates, but thromboembolic risk persists during the recovery phase 7, 8
• Reassess need for continued anticoagulation at 3 months based on EF, thrombus resolution, and rhythm 2, 7