Thromboembolism.

Fatal thromboembolism in pregnancy and the puerperium is becoming less frequent but remains the second commonest cause of maternal death. The mechanism responsible for the pathogenesis is complex and the predisposition to thrombus formation in pregnancy is probably the interaction of several different factors. Because of the risks of anticoagulant therapy, it is important to establish the diagnosis of thromboembolism before commencing treatment using venography and pulmonary angiography when necessary. When anticoagulants are used in pregnancy, coumarin derivatives can be used until 36 weeks and then substituted by heparin; alternatively heparin alone can be given throughout pregnancy. Subcutaneous heparin has no fetal effects and can be used successfully on an outpatient basis. Prevention is always better than cure, and it is essential that well-established preventive measures should be carried out diligently so that the incidence of this rare, but dreaded, complication can be reduced to an absolute minimum.