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Low Molecular Weight Heparin (LMWH) — VTE Prophylaxis/Treatment Pregnancy: Used throughout pregnancy — drug of choice for VTE

Enoxaparin (VTE in Pregnancy)

Brand names: Clexane

Adult dose

Dose: VTE prophylaxis: 40 mg SC OD (standard). Weight-adjusted: <50 kg → 20 mg OD; 50–90 kg → 40 mg OD; 91–130 kg → 60 mg OD; 131–170 kg → 80 mg OD; >170 kg → 0.6 mg/kg OD. Treatment dose (acute VTE): 1 mg/kg SC BD or 1.5 mg/kg OD
Route: Subcutaneous
Frequency: Once or twice daily depending on indication
Max: Treatment: 1.5 mg/kg OD; prophylaxis: weight-banded as above
LMWH of choice for VTE in pregnancy (RCOG Green-top 37a). Commence from 1st trimester. Stop 24h before planned delivery (therapeutic dose) or 12h before (prophylactic). Do not give during labour or within 4h of regional anaesthesia. Restart 4h after spinal needle removal.

Paediatric dose

Route: N/A
Frequency: N/A
Max: N/A
Not applicable in obstetric indication

Dose adjustments

Renal

Reduce dose in severe renal impairment (eGFR <30) — use UFH instead or anti-Xa monitoring

Hepatic

Caution in hepatic impairment

Clinical pearls

  • LMWH of choice in UK pregnancy — does not cross placenta, no teratogenicity
  • High-risk VTE prophylaxis: consider from first trimester in women with prior VTE, thrombophilia, or high-risk features (RCOG Green-top 37a)
  • Anti-Xa monitoring: consider at extremes of weight or renal impairment — target 0.5–1.0 IU/mL (treatment) or 0.2–0.5 IU/mL (prophylaxis) 4h post-dose
  • Regional anaesthesia safety: withhold therapeutic dose 24h, prophylactic dose 12h before neuraxial anaesthesia
  • Transition to UFH at 36 weeks in women at very high VTE risk — allows more flexible reversal peripartum

Contraindications

  • Active major bleeding
  • Thrombocytopenia (HIT)
  • Within 24h of neuraxial anaesthesia/removal (therapeutic dosing)

Side effects

  • Injection site bruising (common)
  • Bleeding
  • Thrombocytopenia (HIT — less common than UFH)
  • Osteoporosis (prolonged use)
  • Hyperkalaemia

Interactions

  • NSAIDs/aspirin — increased bleeding risk
  • Other anticoagulants — additive bleeding

Monitoring

  • Anti-Xa levels (if extremes of weight/renal impairment)
  • Platelet count at day 5–7 (HIT monitoring)
  • Signs of bleeding or thrombosis
  • Renal function

Reference: BNFc; RCOG Green-top 37a VTE in Pregnancy; NICE NG89; BNF. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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