Venous Thromboembolism (VTE) During Pregnancy
NHS Scotland GGC – Clinical Guidelines Thromboembolic Disease during Pregnancy and the Puerperium (605). Last revised: Oct 2017.
RCOG Reducing the Risk of Thrombosis and Embolism during Pregnancy and the Puerperium (Green-top Guideline No. 37a). Last reviewed: Apr 2015.
RCOG Thrombosis and Embolism during Pregnancy and the Puerperium: Acute Management (Green-top Guideline No. 37b). Last revised: Apr 2015.
Prevention of VTE
In practice, a pregnant woman’s VTE risk is assessed using a risk assessment score, with clear documented instructions regarding subsequent steps and management.
Therefore this section outlines only principles-based, exam-related concepts. It would be unnecessary to memorise the entire guideline or every detail below. Instead, it is more important to recognise key VTE risk factors, and to appreciate the choice of anticoagulation and its main indications.
Risk Factors
Risk factors for VTE during pregnancy can be categorised as (non-exhaustive list):
| Pre-existing risk factors |
|
| Obstetric risk factors | Non-labour related:
Labour related:
|
| New onset / transient risk factors |
|
Management
Most important: if the patient had any previous VTE, except a single event related to major surgery → offer prophylaxis throughout antenatal period
- There are multiple additional indications for antenatal prophylaxis but are omitted due to excessive detail
- Key further recommendations are
- If there are 4 or more risk factors → consider antenatal prophylaxis
- If there are 3 risk factors → consider prophylaxis from 28 weeks onwards
Choice of drug:
- 1st line: LMWH (e.g. enoxaparin)
- 2nd line: UFH
Dosing and monitoring:
- Dose is weight based (typically based on actual body weight), the exact dose also depends on risk stratification
- Routine monitoring of anti-Xa level is NOT required
- Routine monitoring of platelet count is NOT required (unless there is a prior exposure to UFH)
Safety:
- LMWH is safe in breastfeeding
- It is worth noting that warfarin is safe in breastfeeding, but NOT in pregnancy (it is highly teratogenic). DOACs are contraindicated in BOTH pregnancy and breasatfeeding.
VTE Assessment and Management
Investigation and Diagnosis
In clinically suspected DVT or PE, treatment with LMWH should be commenced immediately (without awaiting for diagnostic confirmation), unless treatment is strongly contraindicated.
It should then only be stopped, if the diagnosis is excluded by objective testing.
D-dimer testing should NOT be performed in the investigation of VTE in pregnancy.
DVT Suspected
Diagnostic test of choice: leg ultrasound (compression Duplex ultrasound)
PE Suspected
Initial assessment:
- Chest X-ray and ECG (to exclude other differential diagnoses)
- Assess the patient’s leg carefully for features of DVT
Subsequent investigations (if the chest X-ray is normal – i.e. PE is still the top differential diagnosis):
| Scenario | Recommended investigation |
|---|---|
| Clinical features of DVT are present | Perform a leg ultrasound
If a DVT is confirmed:
|
| NO clinical features of DVT | Perform a CTPA or V/Q scan
The exact choice of CTPA vs V/Q scan would depends on:
|
Patients should be advised that compared to CTPA, V/Q scan may carry a slightly increased risk of childhood cancer but is associated with a lower risk of maternal breast cancer.
In both situations, the absolute risk is very small.
Management
1st line: LMWH (e.g. enoxaparin)
- Duration: throughout pregnancy + for at least 6 weeks postnatally + until at least 3 months of treatment has been given in total
- Monitoring
- Routine measurement of peak anti-Xa activity is NOT required, exceptions
- Extreme body weights (<50 kg or >90kg)
- Renal impairment
- Recurrent VTEs
- Routine platelet count monitoring is NOT required
- Routine measurement of peak anti-Xa activity is NOT required, exceptions
IV UFH is the preferred, initial treatment in massive PE with cardiovascular instability.
Warfarin and DOACs are contraindicated during pregnancy.