ObstetricsTier 1Disease (DEADMAN)

Venous thromboembolism, such as pulmonary embolism

Description

Leading direct cause of maternal death in high-income countries
Risk elevated throughout pregnancy, highest in the postpartum period, particularly after caesarean
DVT more often ileofemoral/left-sided in pregnancy (compression of left iliac vein by right iliac artery + gravid uterus)

Virchow's triad, all three amplified by pregnancy
- Hypercoagulability - physiological rise in clotting factors, fall in protein S
- Venous stasis - progesterone-mediated venodilation, mechanical compression by gravid uterus
- Venous injury - delivery (esp. instrumental/caesarean)
Additional risk factors: obesity, age >35, parity >=3, smoking, immobility, prior VTE, thrombophilia, multiple pregnancy, IVF, pre-eclampsia, postpartum haemorrhage, infection

D-dimer not useful - physiologically elevated throughout pregnancy, poor specificity
Compression ultrasound first-line for suspected DVT
Suspected PE: CXR first (also excludes differentials) then CTPA or V/Q scan - do not withhold imaging because of pregnancy, maternal mortality risk outweighs fetal radiation risk at diagnostic doses
- V/Q - lower maternal breast dose, marginally higher fetal dose; CTPA - opposite trade-off; local availability and renal function also guide choice
Wells score not validated in pregnancy - treat on clinical suspicion pending imaging

Treatment (confirmed or high clinical suspicion pending imaging)

LMWH - anticoagulant of choice throughout pregnancy (does not cross placenta)
- Weight-based therapeutic dosing
Warfarin contraindicated - teratogenic (embryopathy 6-12 weeks), crosses placenta -> fetal bleeding risk
DOACs not recommended in pregnancy (insufficient safety data, cross placenta)
Continue therapeutic LMWH throughout pregnancy and at least 6 weeks postpartum, minimum total duration 3 months
Peripartum planning - stop/switch dosing around expected delivery and neuraxial anaesthesia timing (coordinate with anaesthetics)

Prophylaxis - risk-factor based

Individualised risk assessment antenatally and postnatally (each pregnancy reassessed)
Prophylactic LMWH if:
- Prior VTE, OR
- High-risk thrombophilia, OR
- Multiple intermediate risk factors (obesity, age, parity, smoking, pre-eclampsia, prolonged immobility, caesarean, etc - risk factors are cumulative/additive)
Mechanical prophylaxis (compression) if pharmacological contraindicated (active bleeding)

Pre-eclampsia, postpartum haemorrhage, caesarean section (esp. emergency)
Thrombophilia (Factor V Leiden, prothrombin gene mutation, antiphospholipid syndrome, protein C/S/antithrombin deficiency)
Obesity, smoking, multiple pregnancy, ART/IVF pregnancy
Hyperemesis gravidarum (dehydration + immobility)

Untreated PE in pregnancy carries significant mortality - same acuity as non-pregnant PE plus diagnostic delay risk
Post-thrombotic syndrome - chronic leg swelling/pain, more likely after untreated/delayed-treated DVT
Recurrence risk in future pregnancies - informs prophylaxis decisions in subsequent pregnancies regardless of interim anticoagulation status

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