Thromboprophylaxis in pregnancy

Surgical approach (if applicable)

Not an operation: management is obstetric/medical (risk assessment + pharmacological/mechanical prophylaxis).
Where it interfaces with surgery/obstetrics:
- Elective caesarean: plan timing of last LMWH dose; use mechanical methods intra-op; restart LMWH post-op when haemostasis secure.
- Emergency delivery: if recent LMWH, neuraxial may be contraindicated; consider GA; use pneumatic compression; involve haematology/obstetrics early.
- Operative procedures in pregnancy (e.g., cerclage, non-obstetric surgery): coordinate perioperative anticoagulation interruption and VTE prophylaxis.

Anaesthetic management (where relevant)

Type of anaesthesia: neuraxial (spinal/epidural/CSE) preferred for caesarean if anticoagulation timing allows; GA if neuraxial unsafe or urgent.
Airway: if GA, usually ETT (RSI). SGA generally avoided for caesarean except rescue.
Duration: caesarean typically ~45–90 min; neuraxial catheter may be in situ for labour analgesia.
How painful: caesarean—moderate/severe without neuraxial; labour—severe; neuraxial provides excellent analgesia.
Key anaesthetic issue: neuraxial safety windows with LMWH/UFH; avoid spinal/epidural haematoma; document timing of last dose and plan for restart.
If on therapeutic anticoagulation: anticipate higher PPH risk; ensure bloods/IV access; consider cell salvage for caesarean if appropriate; multidisciplinary plan.

Why it matters (epidemiology and physiology)

Pregnancy is a hypercoagulable state (↑ fibrinogen, ↑ factors VII/VIII/X, ↓ protein S, reduced fibrinolysis) + venous stasis (uterine compression) + vascular injury (delivery) → VTE risk rises.
VTE is a leading cause of maternal morbidity/mortality; risk highest in the postpartum period (especially first 6 weeks).
Anaesthetic relevance: balancing VTE prevention vs bleeding/PPH and neuraxial haematoma risk; timing of LMWH around labour and caesarean.

Risk assessment (principles)

Assess VTE risk early in pregnancy, again with any admission/intercurrent illness, intrapartum, and postpartum; document plan and communicate to anaesthesia team.
Risk factors (examples):
- Previous VTE (especially unprovoked or oestrogen/pregnancy-related).
- Thrombophilia: antithrombin deficiency (highest risk), protein C/S deficiency, factor V Leiden, prothrombin gene mutation; antiphospholipid syndrome (APS).
- Obesity, age >35, parity ≥3, smoking, varicose veins, immobility, dehydration, infection, inflammatory disease, nephrotic syndrome, sickle cell disease.
- Obstetric: multiple pregnancy, pre-eclampsia, IVF/assisted reproduction, hyperemesis, prolonged labour, operative delivery, postpartum haemorrhage, caesarean (esp emergency).
Mechanical prophylaxis (graduated stockings / intermittent pneumatic compression) is useful when bleeding risk is high or anticoagulation is paused.

Pharmacological options

LMWH is first-line for prophylaxis and treatment in pregnancy (does not cross placenta; predictable PK; lower HIT/osteoporosis risk than UFH).
UFH: consider when rapid reversal may be needed (very high bleeding risk, near delivery, renal failure) or when neuraxial timing is critical; can be reversed with protamine.
Warfarin: teratogenic (especially weeks 6–12) and fetal bleeding risk; generally avoided in pregnancy but compatible with breastfeeding postpartum.
DOACs: insufficient safety data in pregnancy; generally avoided; not recommended during breastfeeding (agent-specific guidance varies).
Aspirin: used for pre-eclampsia prevention and APS (with heparin) in selected cases; not adequate as sole VTE prophylaxis.

Dosing and monitoring (exam-focused principles)

Prophylactic LMWH: usually fixed or weight-adjusted prophylactic dosing per local guideline (booking weight often used); consider higher doses in obesity.
Therapeutic LMWH: weight-based dosing (e.g., enoxaparin 1 mg/kg BD) per guideline; consider anti-Xa monitoring in extremes of weight, renal impairment, recurrent VTE, or high-risk thrombophilia (local practice varies).
Platelets: check baseline and if clinically indicated; HIT is rare with LMWH but possible (more with UFH).
Renal impairment: LMWH accumulates; consider dose adjustment, anti-Xa monitoring, or UFH.

Neuraxial anaesthesia and anticoagulation timing (core FRCA viva content)

Aim: minimise risk of spinal/epidural haematoma by respecting minimum intervals between anticoagulant dosing and neuraxial needle/catheter manipulation.
LMWH prophylactic dose (typical guidance):
- Wait at least 12 hours from last prophylactic LMWH dose before neuraxial block or epidural catheter removal.
- After neuraxial puncture/catheter removal: delay next LMWH dose for at least 4 hours (and ensure no traumatic/ bloody tap; if traumatic, consider longer delay and senior review).
LMWH therapeutic dose (typical guidance):
- Wait at least 24 hours from last therapeutic LMWH dose before neuraxial block or catheter removal.
- Restart LMWH at least 4 hours after catheter removal/puncture (longer if bleeding risk/traumatic puncture).
UFH (typical guidance):
- Low-dose SC UFH prophylaxis: neuraxial often acceptable with shorter intervals (commonly 4–6 h) and normal coagulation/platelets; follow local policy.
- IV UFH infusion: stop and confirm normal APTT before neuraxial; restart after an appropriate interval once haemostasis assured; follow local policy.
Antiplatelets: low-dose aspirin alone is not usually a contraindication to neuraxial; dual antiplatelet therapy or additional anticoagulants increase risk—seek senior/haematology advice.
Neurological monitoring: after neuraxial in anticoagulated patients, maintain high suspicion for epidural haematoma (new back pain, motor weakness, sensory changes, bladder/bowel dysfunction) → urgent MRI and neurosurgical decompression (time-critical).

Peripartum planning (elective and emergency)

Elective induction/caesarean in women on LMWH: plan last dose to allow neuraxial option; document exact timing; ensure mechanical prophylaxis while anticoagulation is held.
Spontaneous labour while on LMWH: advise patients to omit further LMWH once labour suspected/established and present early; neuraxial depends on time since last dose.
Emergency caesarean with recent LMWH: neuraxial may be contraindicated; proceed with GA if cannot safely delay; use mechanical prophylaxis and restart anticoagulation post-op when safe.
High-risk women near term (e.g., recent VTE, very high-risk thrombophilia): some pathways switch from LMWH to UFH close to delivery to allow shorter neuraxial windows and easier reversal—specialist-led decision.

Postpartum thromboprophylaxis

Postpartum period carries highest VTE risk; reassess after delivery considering mode of delivery, haemorrhage, immobility, infection, and ongoing risk factors.
Restarting LMWH after delivery/CS: when haemostasis is secure and bleeding risk acceptable; coordinate with neuraxial catheter removal timing.
Duration: depends on risk profile (e.g., short course for intermediate risk vs 6 weeks for high risk such as previous VTE)—follow local/RCOG-based policy.
Breastfeeding: LMWH and warfarin are compatible; DOACs generally avoided.

Complications and special situations

Bleeding/PPH: withhold anticoagulation in active bleeding; involve obstetrics/haematology; consider reversal strategies (protamine partially reverses LMWH; fully reverses UFH).
Thrombocytopenia: consider gestational thrombocytopenia vs pre-eclampsia/HELLP vs HIT; if HIT suspected, stop heparin and seek urgent haematology input; use non-heparin anticoagulant.
Neuraxial haematoma: rare but catastrophic; urgent MRI and neurosurgical decompression ideally within hours of symptom onset.
Obesity: increased VTE risk and may need weight-adjusted prophylaxis; ensure correct stocking size and use intermittent pneumatic compression perioperatively.
Regional anaesthesia in anticoagulated parturients: always check timing, dose (prophylactic vs therapeutic), renal function, concurrent antiplatelets, and whether puncture was traumatic.

A woman at 39 weeks is booked for elective caesarean and is on prophylactic LMWH. How do you plan neuraxial anaesthesia safely?

Structure: confirm indication/dose/timing → apply neuraxial timing rules → plan intra/post-op prophylaxis and restart.

Clarify LMWH regimen: agent, dose, time of last dose; confirm it is prophylactic (not therapeutic).
Neuraxial timing: ensure ≥12 h since last prophylactic LMWH before spinal/epidural/CSE.
If epidural catheter used: plan removal when ≥12 h since last prophylactic LMWH; then delay next LMWH ≥4 h after removal.
Use mechanical prophylaxis (IPC) perioperatively while LMWH is held.
Restart LMWH postpartum when haemostasis secure and neuraxial timing permits; document exact times and handover.

A labouring patient has had a therapeutic dose of LMWH 10 hours ago and requests an epidural. What do you do?

Key point: therapeutic LMWH usually requires a 24-hour interval before neuraxial procedures.

Confirm dosing is therapeutic and establish exact timing of last injection.
Explain neuraxial is contraindicated until ≥24 h after last therapeutic LMWH dose (typical guidance) due to epidural haematoma risk.
Offer alternatives: systemic opioids (PCA), remifentanil PCA where appropriate with 1:1 monitoring, nitrous oxide, supportive measures.
If urgent operative delivery required: likely GA if neuraxial unsafe; use mechanical prophylaxis and plan postpartum anticoagulation restart.
Escalate early to consultant obstetric anaesthetist and involve obstetrics/haematology for peripartum anticoagulation strategy.

Outline a risk assessment approach to thromboprophylaxis in pregnancy and postpartum.

Examiners want: repeated assessment points + key risk factors + mechanical vs pharmacological + postpartum emphasis.

Assess at booking, with any admission/intercurrent illness, intrapartum, and postpartum; document and communicate.
Identify major risks: previous VTE, high-risk thrombophilia/APS, prolonged immobility, obesity, caesarean (esp emergency), pre-eclampsia, infection/PPH.
Choose prophylaxis: LMWH for most; mechanical methods when bleeding risk high or anticoagulation paused.
Postpartum: highest risk—ensure reassessment after delivery; decide duration based on risk (often longer for prior VTE/high-risk thrombophilia).

What are the key differences between LMWH and UFH in pregnancy, and when might you choose UFH?

Core comparison: PK predictability, monitoring, HIT/osteoporosis, reversibility, neuraxial planning, renal impairment.

LMWH: predictable dose-response, once/twice daily dosing, lower HIT/osteoporosis risk, minimal monitoring; first-line.
UFH: shorter half-life, can be fully reversed with protamine, easier to stop/adjust; requires APTT monitoring if IV therapeutic.
Choose UFH when: near delivery with need for rapid offset/reversal, very high bleeding risk, renal failure/accumulation risk with LMWH, or specialist pathway for high-risk patients.

A woman on prophylactic LMWH has an epidural in labour. How do you manage catheter removal and restarting LMWH?

They want the two timing rules and documentation/monitoring.

Ensure ≥12 h since last prophylactic LMWH before removing the epidural catheter.
After removal, delay next LMWH dose for ≥4 h (and longer if traumatic insertion/removal or bleeding concerns).
Document times (last LMWH, removal, restart) and provide clear handover to midwifery/obstetrics.
Monitor for neurological symptoms post-removal; escalate immediately if concerns.

How would you manage an emergency caesarean section in a woman who received prophylactic LMWH 6 hours ago?

Key: neuraxial likely contraindicated; choose safest anaesthetic; mechanical prophylaxis; restart later.

Confirm timing/dose and urgency category; if only 6 h since prophylactic LMWH, neuraxial usually contraindicated (needs ≥12 h).
Proceed with GA if cannot delay; RSI with ETT; optimise aspiration prophylaxis and haemodynamic management.
Use intermittent pneumatic compression intra- and post-operatively.
Post-op: restart LMWH when haemostasis secure and neuraxial considerations irrelevant (no catheter) but still avoid early dosing if bleeding risk/PPH.

What symptoms and signs suggest an epidural haematoma, and what is your immediate management?

Time-critical emergency: recognise early, stop anticoagulants, urgent imaging and decompression.

Symptoms/signs: severe back pain, new motor weakness, sensory loss, radicular pain, saddle anaesthesia, bladder/bowel dysfunction, unexpected prolonged block.
Immediate actions: stop anticoagulants; urgent senior anaesthetic review; full neuro exam and documentation; urgent MRI spine.
Early neurosurgical/spinal surgical referral; decompression is time-dependent (aim within hours).

Discuss thromboprophylaxis after caesarean section.

Examiners want: caesarean increases risk, mechanical + LMWH, timing with haemostasis and neuraxial, duration depends on risk.

All: early mobilisation + hydration; consider mechanical prophylaxis perioperatively (especially emergency CS or additional risk factors).
LMWH postpartum: start when haemostasis secure; coordinate with neuraxial catheter removal timing (≥4 h after removal; and ensure appropriate interval since last dose before removal).
Duration: risk-stratified (short course for intermediate risk; up to 6 weeks for high risk such as previous VTE).

A pregnant woman has suspected pulmonary embolism. What is the immediate anticoagulation approach and what are the anaesthetic implications if she needs urgent delivery?

In FRCA vivas, focus on immediate treatment, MDT, and neuraxial implications rather than diagnostic algorithms.

If PE strongly suspected: start therapeutic anticoagulation (usually LMWH) unless contraindicated; involve obstetrics/respiratory/haematology.
If urgent delivery needed: therapeutic LMWH usually precludes neuraxial for 24 h; GA may be required; consider haemodynamic/respiratory optimisation and ICU involvement.
Use mechanical prophylaxis and plan postpartum anticoagulation continuation; consider UFH pathway if rapid reversibility needed (specialist decision).

What are the maternal and fetal considerations of anticoagulants used in pregnancy (LMWH, UFH, warfarin, DOACs)?

They want placental transfer/teratogenicity, breastfeeding, and maternal adverse effects.

LMWH/UFH: do not cross placenta; safe for fetus; maternal risks include bleeding, (rare) HIT, osteoporosis (more with UFH).
Warfarin: crosses placenta; teratogenic (esp weeks 6–12) and fetal bleeding; generally avoided in pregnancy but safe in breastfeeding.
DOACs: limited safety data; generally avoided in pregnancy and breastfeeding.

Discuss the management of anticoagulation in a pregnant patient requesting neuraxial analgesia/anaesthesia.

Common FRCA theme: safe neuraxial timing + alternatives + documentation + haematoma recognition.

Take a focused history: indication for anticoagulation, agent, dose (prophylactic vs therapeutic), timing of last dose, renal function, other antiplatelets/anticoagulants, bleeding history.
Apply neuraxial windows: prophylactic LMWH ≥12 h; therapeutic LMWH ≥24 h; UFH depends on regimen (often shorter for low-dose SC).
Plan catheter management: removal timing and restart (commonly ≥4 h after removal/puncture).
If neuraxial contraindicated: offer alternative labour analgesia; if operative delivery required, consider GA and mechanical prophylaxis.
Safety net: neurological monitoring and escalation pathway for suspected neuraxial haematoma.

Outline thromboprophylaxis for caesarean section and the implications for neuraxial techniques.

Typical exam expectation: risk stratification, mechanical measures, LMWH timing around spinal/epidural and catheter removal.

Recognise caesarean (especially emergency) increases VTE risk; add patient-specific risk factors (obesity, pre-eclampsia, immobility, PPH).
Use mechanical prophylaxis perioperatively (IPC) and encourage early mobilisation.
LMWH postpartum: start when haemostasis secure; ensure neuraxial catheter removal timing is compliant; document and handover.
Duration is risk-based; high-risk patients may require extended prophylaxis (often 6 weeks).

Describe the diagnosis and management of epidural/spinal haematoma in an obstetric patient.

Classic FRCA emergency scenario: recognition + urgent imaging + decompression.

Risk factors: anticoagulation (LMWH/UFH), traumatic puncture, multiple attempts, coagulopathy, concurrent antiplatelets.
Presentation: severe back pain, evolving motor/sensory deficits, sphincter dysfunction, unexpected prolonged/patchy block.
Management: stop anticoagulants; urgent MRI; immediate neurosurgical referral; decompression urgently (time-dependent neurological outcome).
Prevention: adhere to neuraxial timing guidance; minimise traumatic attempts; careful documentation and communication.

Compare LMWH and UFH in pregnancy and discuss reversal of anticoagulation in the setting of obstetric haemorrhage.

Often examined as a pharmacology + obstetric haemorrhage interface question.

LMWH: predictable, lower HIT/osteoporosis; partial reversal with protamine (incomplete).
UFH: shorter half-life; full reversal with protamine; easier to titrate/stop.
In PPH: prioritise haemorrhage control; hold anticoagulants; consider protamine (especially for UFH); involve haematology for complex cases.