Canterbury DHB


Pregnancy & Thrombosis

Features of pregnancy that require special consideration are:

In This Section



Investigation for DVT/PE

Prophylaxis of DVT/PE


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

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.



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 (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.

About this Canterbury DHB document (5210):

Document Owner:

Not assigned (see Who's Who)

Last Reviewed:

August 2016

Next Review:

August 2018


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Topic Code: 5210