Canterbury DHB

Pregnancy & Thrombosis

Features of pregnancy that require special consideration are:

• High incidence of venous thromboembolism especially in puerperium.
• Compression of iliac veins by foetus.
• Teratogenic effects of warfarin

Prophylaxis

Select LMWH dose on basis of moderate or high-risk assessment.

• Women with a Thrombotic History but no known Thrombophilic Abnormality

  Start prophylactic heparin (Tinzaparin) at a timepoint, which may be based on previous thrombotic history. Continue thromboprophylaxis for six weeks post partum.

• Women with a Thrombotic History and Known Thrombophilic Abnormality

  AT III deficiency (heterozygous)

  Consider therapeutic doses of heparin throughout pregnancy followed by six weeks of warfarin or a continuation of the heparin.

  Protein C/S deficiencies, FV Leiden (heterozygous) and anti-phospholipid antibodies

  Consider prophylactic doses of heparin during first and second trimesters followed by therapeutic doses of heparin during the third trimester and warfarin (or a continuation of the heparin) for six weeks after delivery.

• Women with Thrombophilic Abnormality but no Thrombotic History

  AT III deficiency (heterozygous)

  Consider therapeutic doses of heparin throughout pregnancy followed by six weeks of warfarin (or a continuation of the heparin).

  Protein C/S deficiencies and FV Leiden (heterozygous)

  Start heparin and warfarin after delivery and continue warfarin for six weeks.

  Anti-phospholipid antibodies

  Aspirin 75mg daily throughout pregnancy. Heparin may be utilised to try to improve pregnancy outcome in selected patients. Start heparin and warfarin after delivery and continue warfarin for six weeks.

• Women with a Thrombotic History and Post Phlebitic Limb

  For women with persistent evidence of venous insufficiency or obstruction following previous DVT consider prophylactic doses of heparin during the first and second trimesters followed by therapeutic doses during the third trimester and warfarin (or a continuation of the heparin) for six weeks after delivery.

Prosthetic heart valves

Warfarin therapy carries a risk of teratogenesis which is maximum at 6 - 12 weeks gestation. Many authorities recommend substitution of dose adjusted heparin for warfarin at least until week 12 and again close to term to avoid delivery of an anticoagulated foetus. When heparin is used, therapeutic doses (see DVT treatment) of low molecular weight heparin (with monitoring) are recommended and usually aspirin should be used in addition.

Complications

Osteoporosis

Osteoporosis with vertebral fractures has been reported in women receiving prolonged heparin therapy. Where possible, bone densitometry should be performed prior to pregnancy. No clinical trials of preventative treatment are available. Calcitriol may be used to try to prevent bone loss in at risk patients.

Thrombocytopenia

Thrombocytopenia (HIT) is a rare complication of the use of all forms of heparin though less frequent with LMWH. Check platelet count monthly and if any bleeding or clotting episode. Mild thrombocytopenia may occur in normal pregnancy.

Epidural anaesthesia

See surgical section.

Topic Code: 5210