Protein C is thought to play a key role in the regulation of hemostasis, and its deficiency has been associated with an increased risk of thromboembolism. Protein C-deficient women are at particular risk of developing thromboembolic complications during pregnancy and delivery. The incidence of thromboembolic events is estimated to be 500-1000 times higher than in normal women. We report the case of a 26-year-old woman with previous iliofemoral deep vein thrombosis who experienced a successful pregnancy and delivery despite severe congenital protein C deficiency (protein C antigen and activity 25%). She was anticoagulated with heparin during the second part of her pregnancy. Our observation suggests that ambulatory full-dose subcutaneous heparin therapy during pregnancy constitutes adequate prevention. However, definite guidelines will require more extensive studies.