Background

• VTE (DVT + PE) is a leading direct cause of maternal death in the UK.

• Risk is 4–6× higher in pregnancy and highest postpartum (esp. first 3 weeks).

• Caesarean section, obesity, and age >35 years are major contributors.

• LMWH reduces VTE risk by 60–70% and is safe in pregnancy and breastfeeding.

2️⃣ Risk Assessment

• All women: documented VTE risk assessment prepregnancy or early pregnancy, repeated:

  • If hospitalised or new problems arise

  • Intrapartum/immediate postpartum

• Use Appendix I & Table 1 for risk scoring.

Timing of LMWH prophylaxis:

3️⃣ Major Risk Factors for VTE

Pre-existing:

• Previous VTE

• Thrombophilia (hereditary or acquired)

• Medical comorbidities: SLE, IBD, nephrotic syndrome, sickle cell disease, heart disease

• Obesity (BMI ≥30)

• Age >35 years

• Smoking

• Parity ≥3

Obstetric:

• Multiple pregnancy

• Pre-eclampsia

• Caesarean section (especially emergency)

• Prolonged labour, operative delivery

• Postpartum haemorrhage

• Preterm birth or stillbirth

New/Transient:

• Surgery during pregnancy

• Hyperemesis gravidarum

• Ovarian hyperstimulation syndrome

• IVF pregnancy

• Hospital admission or immobility ≥3 days

• Infection

• Long-distance travel (>4 hrs)

4️⃣ Women with Previous VTE

Antenatal prophylaxis:

• All previous VTE (except single event after major surgery, no other risk) → LMWH throughout pregnancy

• All previous VTE → 6 weeks postpartum LMWH or warfarin

High-risk (antithrombin deficiency / APS / recurrent VTE):

• Higher-dose LMWH (50–100%) during pregnancy + 6 weeks postpartum

• Managed by haematologist

If on warfarin: switch to LMWH as soon as pregnancy confirmed, ideally before 6 weeks.

5️⃣ Asymptomatic Thrombophilia

6️⃣ Timing of LMWH

• Start early if previous VTE or high risk.

• First-trimester triggers:

  • Hyperemesis

  • Ovarian hyperstimulation

  • IVF + 3 other risk factors → LMWH early.

7️⃣ Labour and Delivery

• Stop LMWH at onset of labour or bleeding.

• Regional anesthesia:

  • Avoid for 12 hrs after prophylactic dose

  • Avoid for 24 hrs after therapeutic dose

  • Restart LMWH 4 hrs after removal of epidural/spinal catheter.

• First postnatal LMWH: as soon as possible after birth (if no PPH or spinal used).

• If high bleeding risk: use stockings / pneumatic devices / UFH.

8️⃣ Postnatal Thromboprophylaxis

All LSCS: 10 days LMWH
Elective LSCS: 10 days LMWH if any other risk factors

9️⃣ Agents

• LMWH – drug of choice

  • Weight-based dosing (use booking or latest weight)

  • No routine anti-Xa or platelet monitoring needed

  • Reduce dose in renal impairment

  • Safe in breastfeeding

• UFH – for very high risk or need for rapid reversal

• Warfarin – postpartum only (safe in lactation)

• NOACs (DOACs) – contraindicated in pregnancy and lactation

• Aspirin – not for VTE prophylaxis

• Anti-embolism stockings – adjunct or alternative when LMWH contraindicated

10️⃣ Contraindications to LMWH

• Active bleeding

• Major risk of haemorrhage

• Known hypersensitivity to heparin

• Recent or ongoing epidural/spinal anaesthesia

11️⃣ Key MRCOG Takeaways

• All women → early & repeated VTE risk assessment.

• LMWH mainstay for prevention – dosing & timing matter most in exams.

• Regional anaesthesia rules often tested (12- and 24-hour gaps).

• Postnatal thromboprophylaxis questions are high yield.

• Previous VTE + thrombophilia always require consultant-led care.

📘 Prepared by MedisPrep for MRCOG Study Reference Only

For complete recommendations, always refer to the full RCOG Green-top Guideline No. 37a (2015).