What is the most appropriate management for a healthy primigravida with a history of previous deep venous thrombosis (DVT)?

Management of Primigravida with History of Previous DVT

A healthy primigravida with a history of previous deep venous thrombosis should receive prophylactic or intermediate-dose low-molecular-weight heparin (LMWH) throughout pregnancy, making Enoxaparin (Option C) the most appropriate choice among the options provided.

Rationale for Anticoagulation in Pregnancy

Pregnancy increases VTE risk 5-fold compared to non-pregnant women, and a history of prior DVT significantly elevates recurrence risk. 1 The key principle is that vitamin K antagonists (warfarin) must be avoided during pregnancy due to placental crossing, embryopathy risk between 6-12 weeks' gestation, and fetal bleeding complications including intracranial hemorrhage at delivery. 1

Why LMWH (Enoxaparin) is Preferred

• LMWH does not cross the placenta and is not associated with embryopathy or fetal bleeding, making it the anticoagulant of choice during pregnancy 1, 2
• The American College of Chest Physicians recommends LMWH over unfractionated heparin for prevention and treatment of VTE in pregnancy 2
• For pregnant women with a single prior episode of DVT, guidelines recommend antepartum prophylactic or intermediate-dose LMWH followed by postpartum anticoagulants 2

Why Other Options Are Inappropriate

• Aspirin (Option A): Insufficient for VTE prophylaxis in patients with prior DVT; aspirin is reserved for antiphospholipid syndrome with pregnancy loss, not DVT prevention 2
• Heparin (Option B): While unfractionated heparin is acceptable, LMWH is preferred due to superior safety profile, less frequent dosing, and no monitoring requirements 2, 3
• No anticoagulant (Option D): Unacceptable given 5-fold increased VTE risk in pregnancy and history of prior DVT 1

Specific Management Algorithm

For a healthy primigravida with one prior DVT episode:

• Initiate prophylactic-dose LMWH (enoxaparin 40 mg subcutaneously once daily) or intermediate-dose LMWH as soon as pregnancy is confirmed 2
• Continue LMWH throughout entire pregnancy 2
• Extend anticoagulation for at least 6 weeks postpartum, with minimum total duration of 6 months 2, 4
• If the prior DVT was associated with a transient risk factor no longer present, clinical surveillance antepartum with postpartum prophylaxis alone may be considered, but given the question presents a "healthy" patient without specifying the prior DVT trigger, prophylactic LMWH is the safer approach 2

Dosing Considerations

• Prophylactic-dose enoxaparin: 40 mg subcutaneously once daily 2
• Intermediate-dose enoxaparin: Weight-adjusted dosing (typically 0.5-1 mg/kg once daily) 2
• Therapeutic-dose enoxaparin: 1 mg/kg twice daily (reserved for acute VTE during pregnancy) 2, 4

Critical Pitfalls to Avoid

• Never use warfarin or direct oral anticoagulants during pregnancy due to teratogenicity and placental crossing 1, 2
• Do not rely on aspirin alone for VTE prophylaxis in patients with prior DVT 2
• Do not discontinue anticoagulation immediately postpartum; the postpartum period carries highest VTE risk, requiring continuation for at least 6 weeks 2, 4
• Ensure total anticoagulation duration meets minimum 6-month threshold when combining antepartum and postpartum therapy 2

Delivery Management

• Temporarily interrupt LMWH when spontaneous labor begins or 24 hours before planned delivery to allow for neuraxial anesthesia if desired 4
• Resume LMWH 6-12 hours after vaginal delivery or 12-24 hours after cesarean section 4
• LMWH use does not preclude breastfeeding 4