Low Molecular Weight Heparin (Pregnancy VTE)

How it works

It potentiates antithrombin, producing predominantly anti-factor Xa activity that inhibits the coagulation cascade and clot formation.

Prescribing in practice

• It is the anticoagulant of choice in pregnancy because it does not cross the placenta, unlike warfarin which is teratogenic; plan dose timing carefully around regional anaesthesia and delivery to reduce bleeding and spinal-haematoma risk.
• Dosing is weight-adjusted in pregnancy and may need review as weight changes; consult current obstetric guidance.
• Avoid in active major bleeding, and use with caution in renal impairment, recent haemorrhagic stroke, and a history of heparin-induced thrombocytopenia.

Monitoring

Monitor for bleeding and, where indicated by renal impairment or extremes of weight, consider anti-Xa level checks alongside platelet review per local protocols.

Counselling the patient

• You will be taught how to give the subcutaneous injection and how to rotate sites and dispose of sharps safely.
• Report unusual bruising, bleeding, or blood in urine or stool.
• Tell the obstetric and anaesthetic team when you last had an injection if labour starts or before any planned delivery.

Evidence & guidelines

RCOG Green-top guidance (GTG 37a/37b) supports low molecular weight heparin as the agent of choice for thromboprophylaxis and treatment of VTE in pregnancy.