Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), remains a leading direct cause of maternal mortality in the UK. Pregnancy and the postpartum period are physiologically hypercoagulable states. Early recognition, appropriate investigation, and prompt anticoagulation are essential to prevent maternal morbidity and mortality.

📊 Epidemiology

Incidence: ~1–2 per 1000 pregnancies
Risk is 5–10× higher than in non-pregnant women
Highest risk: first 6 weeks postpartum
Most antenatal DVTs occur in the left leg (iliac vein compression by gravid uterus)

🧬 Pathophysiology - Virchow’s Triad in Pregnancy

Hypercoagulability:
- ↑ Clotting factors VII, VIII, X, fibrinogen
- ↓ Protein S
- Reduced fibrinolysis
Venous Stasis:
- Uterine compression of pelvic veins
- Reduced venous return
Endothelial Injury:
- Delivery and caesarean section
- Postpartum vascular trauma

⚠️ Risk Factors

Previous VTE
Thrombophilia (Factor V Leiden, Prothrombin mutation, APS)
Obesity
Age >35 years
Multiple pregnancy
Immobility
Caesarean section
Sepsis
Postpartum haemorrhage
Severe hyperemesis

🩺 Clinical Presentation

New or worsening dyspnoea
Pleuritic chest pain
Tachycardia out of proportion to gestation
Unilateral leg swelling/pain
Syncope (concerning)
Hypoxia
Shock (massive PE)

Symptoms may overlap with normal pregnancy physiology - clinical suspicion must remain high.

🧮 Diagnostic Principles

Do NOT use Wells score or D-dimer alone to exclude PE in pregnancy. D-dimer rises physiologically during gestation.

📋 Diagnostic Pathway (NICE NG158 + RCOG aligned)

Step	Action
1️⃣ Suspected DVT	If unilateral leg symptoms → Bilateral compression ultrasound. If DVT confirmed → Treat as PE (no chest imaging required).
2️⃣ Chest X-Ray	Perform CXR in all suspected cases. Used to guide imaging modality.
3️⃣ Normal CXR	Offer V/Q scan (lower breast radiation).
4️⃣ Abnormal CXR	Offer CTPA.
5️⃣ Imaging Delayed	Start treatment-dose LMWH immediately.

🖥️ Imaging Explained

CXR: Usually normal; helps determine V/Q vs CTPA
V/Q Scan: Detects ventilation-perfusion mismatch; preferred if CXR normal
CTPA: Direct visualisation of clot; preferred if CXR abnormal
Modern imaging delivers very low fetal radiation exposure. Maternal survival takes priority.

💊 Treatment

First-Line: Low Molecular Weight Heparin (LMWH)

Enoxaparin: 1 mg/kg twice daily
Dalteparin: 200 units/kg once daily (max 18,000 units)
Adjust for renal impairment
LMWH does not cross the placenta and is safe in pregnancy.

Duration

Minimum 3 months total treatment
Continue for at least 6 weeks postpartum

Avoid

DOACs (Apixaban, Rivaroxaban)
Warfarin (teratogenic in pregnancy)

🚨 Massive PE in Pregnancy

Hypotension (SBP <90 mmHg) or shock
Urgent senior and multidisciplinary input
Consider thrombolysis in life-threatening cases
Maternal survival takes precedence

🍼 Postpartum Considerations

Highest VTE risk: first 6 weeks postpartum
Continue LMWH during this period
Breastfeeding safe with LMWH and warfarin
Avoid DOACs during breastfeeding

🔎 Unprovoked PE in Pregnancy

Screen for thrombophilia only if strong history or unusual presentation
Plan thromboprophylaxis in future pregnancies

🧠 Clinical Pearls

Do not rely on D-dimer to exclude PE
Ultrasound first if DVT symptoms
CXR guides imaging choice
LMWH is the cornerstone of treatment
Continue anticoagulation postpartum
Massive PE requires urgent senior involvement

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