Pregnancy is a hypercoagulable state with an increased risk of deep venous thrombosis (DVT) and pulmonary embolism (PE).
All clotting factors increase during pregnancy, apart from factor XI and XIII. Stasis in the lower limb vessels also increases due to compression of the iliac veins by the gravid uterus.
The most common site of thrombosis in pregnancy is the left ilio-femoral vein due to anatomical compression by the right common iliac artery over the pelvic brim (May-Thurner syndrome).
DVT is most common in the post-operative period, and is 9 times more common following caesarean delivery than vaginal delivery.
Factors contributing to venous thromboembolism in pregnancy
| Component of Virchow’s triad | Factors |
|---|---|
| Hypercoagulability | Estrogen increases the production of fibrinogen, factor VII, IX and X. There is also resistance to protein C in the 2nd and 3rd trimester and reduced activity of protein S and Antithrombin III. The levels of fibrinolysis inhibitors also increases. |
| Stasis | Compression of the iliac veins by the gravic uterus and hypovolemia due to hyperemesis gravidarum or hemorrhage post-partum. Immobility post-partum may also contribute to stasis |
| Endothelial injury | Endothelial injury from pre-eclampsia, puerperal sepsis, placental abruption and even delivery itself |
Risk factors for thromboembolism in pregnancy
| Category | Risk factors |
|---|---|
| Pre existing risk factors | Maternal age > 35 years, thrombophilia, obesity (> 80 kg), history of thromboembolism, severe varicose veins, smoking, malignancy |
| Pregnancy-related risk factors | Multiple gestation, pre-eclampsia, grand multiparity, caesarean delivery (especially emergency), damage to pelvic veins, sepsis, prolonged bed rest |
| Transient risk factors | Dehydration, hyperemesis, sepsis, long-distance travel |
- Risk factors for Venous Thromboembolism in Pregnancy – (In Pregnancy Variable Antenatal FactorS Often Indicate Low Molecular Heparin Prophylaxis)
- Immobility
- Parity ≥ 3
- Varicose veins (gross)
- Age > 35 years
- Family history of VTE
- Smoker
- Obesity
- IVF conception
- Low-risk thrombophilia
- Multiple pregnancies
- Signs and symptoms of deep venous thrombosis
- Symptoms are often unilateral
- Pain
- Swelling
- Tenderness
- Redness
- Leg circumference discrepancy of > 3 cm in the affected leg (measured 10 cm from the ischial tuberosity or 20 cm from the ASIS)
- Symptoms are often unilateral
- Signs and symptoms of pulmonary embolism
- Difficulty in breathing
- Cough
- Hemoptysis
- Chest pain
- Hypoxia
- Tachycardia
- Raised respiratory rate
- Low-grade fever
- Hypotension
- Differentials
- Cellulitis
- Superficial thrombophlebitis (has a palpable cord)
- Varicose veins
- Lymphedema
- Compartment syndrome
- Ruptured popliteal cyst
- Investigations
- Doppler ultrasound of the lower limb to diagnose DVT. Repeat negative ultrasound on day 3 and 7 in high-risk patients.
- Venography is ****a more invasive and expensive alternative to doppler ultrasound
- Chest X-ray and EKG are the initial investigations for patients with suspected pulmonary embolism
- CT-pulmonary angiogram (CTPA) or Ventilation-perfusion (VQ) scan for definitve diagnosis of pulmonary embolism. CTPA is preferred if there is an abnormal chest X-ray. It carres a high risk of breast cancer for the mother.
- D-dimer is ****not useful since pregnancy causes a rise in D-dimer
- aPTT to ensure the patient is accurate ly heparinized
- Adequate heparinization = aPTT 1.5-2.5
- Treatment
- Adequate hydration
- Limb elevation
- Bed rest
- Analgesia
- Elastic stockings
- Early ambulation post-operative
- IV unfractionated heparin (UFH)
- Check for adequate heparinization with aPTT
- Switch to SC LMWH once acute phase is over
- Thrombolysis or surgical embolicteomy for pulmonary embolism