VTE

Question 1

Why is pregnancy prothrombotic?

Answer 1

All three elements of Virchow’s triad:

Stasis: Uterine compression of IVC/iliac veins, progesterone-mediated venodilation
Hypercoagulability: ↑ Factors I (fibrinogen), VII, VIII, X, vWF; ↓ Protein S; ↑ PAI-1/2; resistance to activated protein C
Endothelial injury: Delivery (especially CS), instrumentation
Risk increases throughout pregnancy; highest in the puerperium (first 6 weeks post delivery)

Question 2

When is VTE risk assessment performed?

Answer 2

At booking (first antenatal visit)
At each admission to hospital
Intrapartum
Postnatal (within 6 hours of delivery)
If clinical situation changes (immobilisation, intercurrent illness, surgery)

Question 3

List the risk factors for VTE in pregnancy

Answer 3

Pre-existing:

Previous VTE (most significant)
Thrombophilia (Factor V Leiden, prothrombin 20210A, protein C/S deficiency, antithrombin III deficiency, antiphospholipid syndrome)
Medical comorbidities (nephrotic syndrome, SLE, cancer, sickle cell, inflammatory conditions, heart failure)
Age >35
Obesity (BMI ≥30)
Parity ≥3
Smoking
Varicose veins
Paraplegia
Family history of VTE
Obstetric:

Multiple pregnancy
Pre-eclampsia
CS (especially emergency)
Prolonged labour (>24 hours)
Instrumental delivery
Stillbirth
Preterm birth
PPH requiring surgery/transfusion
Transient:

Hyperemesis
Dehydration
OHSS (ovarian hyperstimulation syndrome)
Long-distance travel (>4 hours)
Surgical procedure in pregnancy
Immobility (bed rest ≥3 days)
Current systemic infection

Question 4

What VTE prophylaxis is given?

Answer 4

LMWH (enoxaparin, dalteparin, or tinzaparin) — prophylactic dose, weight-adjusted
Start from first trimester if previous unprovoked/oestrogen-related VTE or high risk
Start at 28 weeks if total risk score warrants it
Postnatal: Give to all women having CS (minimum 10 days); longer (6 weeks) if additional risk factors
TED stockings — additional measure for hospital inpatients
Early mobilisation encouraged

Question 5

How is suspected DVT in pregnancy investigated?

Answer 5

Compression/duplex USS of affected leg — first-line
If negative but high suspicion → repeat USS in 3-7 days or consider whole-leg USS / MRI
D-dimer is NOT reliable in pregnancy (physiologically elevated)
Left leg DVT more common in pregnancy (left iliac vein compressed by right iliac artery crossing over it)
If iliofemoral DVT suspected and USS inconclusive → MR venography

Question 6

How is suspected PE in pregnancy investigated?

Answer 6

ABC assessment, supplemental O2
Start treatment-dose LMWH before investigations if clinical suspicion is high
CXR first
ECG (sinus tachycardia, right heart strain — S1Q3T3 is classic but rare)
ABG (hypoxia, hypocapnia, respiratory alkalosis)
Bloods: FBC, U&Es, LFTs, coagulation
Then:
If CXR normal → V/Q scan (preferred — lower breast radiation dose)
If CXR abnormal → CTPA (preferred)
CTPA has higher breast radiation but more definitive; V/Q scan delivers slightly more fetal radiation
If massive PE → consider echocardiography and involve ICU/haematology

Question 7

How is confirmed VTE in pregnancy treated?

Answer 7

Treatment-dose LMWH (e.g., enoxaparin 1mg/kg BD or 1.5mg/kg OD)
Continue for remainder of pregnancy + at least 6 weeks postpartum (minimum total duration 3 months from diagnosis)
Monitor anti-Xa levels in extremes of weight, renal impairment
Peripartum management:
Stop LMWH when labour starts or 24 hours before planned CS/induction
Regional anaesthesia safe 12 hours after prophylactic dose, 24 hours after treatment dose
Resume LMWH 4-6 hours after vaginal delivery or 6-12 hours after CS (unless concerns about haemorrhage)
Postnatal: Can switch to warfarin (target INR 2-3) — safe in breastfeeding
Overlap LMWH with warfarin until INR >2 for 2 consecutive days
DOACs (rivaroxaban, apixaban) — CONTRAINDICATED in pregnancy and breastfeeding
Unfractionated heparin — may be used peripartum (short half-life, reversible with protamine)
IVC filter — considered if recurrent PE despite anticoagulation or if contraindication to anticoagulation
Graduated compression stockings for at least 2 years post-DVT (reduce post-thrombotic syndrome)