Pregnancy is what we consider a hypercoagulable state as this is a physiological mechanism to prevent haemorrhage after delivery. The mechanism behind the hypercoagulability induced in pregnancy is multi-factorial. Some factors include:
- Increased concentrations of clotting factors (specifically factors I, II, VII, VIII, IX and XII)
- Decreased concentrations of protein S as well as resistance to protein C (both clotting regulators) and alterations to the fibrinolytic pathway.
- Increased pressure on the vena cava by the uterus which slows down venous return and increases the likelihood for coagulation.
⚠️ Risk factors
The risk factors are important to note and they can be divided into pre-existing, obstetric and transient risk factors:
Pre-existing
- Previous VTE
- Thrombophilias - both heritable and acquired.
- Comorbidities - such as cancer, cardiac failure, SLE, IBD, nephrotic syndrome, diabetes mellitus, sickle cell disease.
- Age >35 years
- BMI >30
- Parity >3
- Gross varicose veins
- Paraplegia
Obstetric
- Multiple pregnancy
- Pre-eclampsia
- C-section
- Prolonged labour
- Stillbirth
- Preterm birth
- Postpartum haemorrhage >1 litre
Transient
- Surgery
- Hyperemesis/dehydration
- Ovarian hyperstimulation syndrome
- Immobility >3 days
- Systemic infection
- Long-distance travel >4 hours
😷 Presentation
The presentation is no different to that of a deep vein thrombosis or pulmonary embolism outside of pregnancy.
- Unilateral calf/thigh swelling and pain
- Redness
- Warmth
- Dilated superficial veins
- Unilateral/asymmetrical pitting oedema
- Tachypnoea
- Dyspnoea
- Pleuritic chest pain
- Tachycardia
- Haemoptysis
- Fever
- Syncope
- Haemodynamic instability
🔍 Investigations
Investigations for DVT:
- Duplex USS with interim anticoagulation in the form of low molecular weight heparin (LMWH).
- If negative but a high level of suspicion remains → repeat on days 3 and 7 and discontinue anticoagulation.
- If negative and there is a low level of clinical suspicion → discontinue anticoagulation.
💡 D-dimers are not useful in pregnancy and should not be done as pregnancy normally raises D-dimer values anyways. This is why we repeat the ultrasound instead of performing a D-dimer as we tend to do normally.
🫁 Investigations for PE:
- If the woman presents with signs and symptoms of acute PE → ECG and chest X-ray.
- Suspected PE + signs of DVT → duplex USS.
- If duplex confirms DVT → no further investigations required for PE.
- Suspected PE + no signs of DVT → V/Q scan or CTPA.
- Abnormal X-ray + suspicion of PE → CTPA is preferred to V/Q scan.
Throughout the investigations, anticoagulant treatment should be continued.
- CTPA carries a risk of breast cancer for the mother.
- V/Q scan carries a risk of childhood cancer for the foetus.
In both cases the absolute risk is very small and the scans should be carried out.
🧰 Management
Thromboprophylaxis is given in the from of low molecular weight heparin (LMWH) such as enoxaparin, dalteparin and tinzeparin.
If the woman has a history of previous VTE → begin thromboprophylaxis as early in pregnancy as practical.
If the lady has no history of previous VTE but has 4 other risk factors → begin thromboprophylaxis as early as practical until 6 weeks postnatally.
If the lady has no history of previous VTE but has 3 other risk factors → begin thromboprophylaxis at 28 weeks gestation until 6 weeks postnatally.
Women should stop injecting LMWH once they begin labour or if they have any vaginal bleeding. It should be continued once again as soon as possible after delivery if there is no postpartum haemorrhage and if regional anaesthesia has not been used.
🥇 The management of VTE in pregnancy is simply LMWH. The dose is based on the weight of the lady at the booking appointment.
Treatment should be started immediately once VTE is suspected and should only be stopped once the diagnosis is excluded.
If the diagnosis is confirmed, then treatment should continue until 6 weeks postnatally or 3 months of treatment in total if that is longer. The prolonged use of LMWH (i.e. more than 12 weeks) decreases the risk of post-thrombotic syndrome.
After delivery, we can potentially switch the LMWH → DOAC or warfarin. However, warfarin should be avoided until at least the 5th day (and longer if at risk of PPH).
🚨 Managing life-threatening PE in pregnancy/puerperium:
Senior physicians, obstetricians and radiologists should manage any woman with cardiovascular compromise due to PE in pregnancy/puerperium. Options for treatment include:
- 🥇 IV unfractionated heparin
- Thrombolysis
- Surgical embolectomy
🚨 Complications
- Post-thrombotic syndrome - venous hypertension that leads to venous ulceration and its associated features (pain, swelling, lipodermatosclerosis, hyperpigmentation etc.). It is a form of chronic venous insufficiency secondary to DVT.
- Maternal death - VTE is the leading cause of maternal death during or up to six weeks after the end of pregnancy.
- Recurrence of VTE