BACKGROUND Complications of pregnancy, including thrombosis and increased fetal loss, have been described in women with heterozygous protein C deficiency. METHODS We report an unusual case of umbilical cord thrombosis, acute renal failure, and cutaneous venous thrombosis associated with severe protein C deficiency in the heterozygous infant of a normal mother. Repeated infusions of protein C concentrate made successful heparinization of the infant possible, with the subsequent resolution of cutaneous thrombosis and improvement of renal status. CONCLUSIONS Heterozygous protein C deficiency in the fetus may result in perinatal thrombosis, which can be treated with viral-inactivated protein C concentrate. Heterozygous protein C deficiency should be considered in cases of fetal compromise or death associated with umbilical vein thrombosis.