A 32-year-old white woman with a history of 2 episodes of abruptio placentae was found to have congenital hypofibrinogenemia. She had no bleeding difficulties except when pregnant. The patient's sisters and her mother also had reduced fibrinogen levels. Results of fibrinogen measurement by clotting assays and immunologic studies were similar. Immunoelectrophoresis, molecular weight of fibrinogen chains, cross-linking by factor XIII, carbohydrate staining, and sialic acid quantitation were all normal, suggesting the diagnosis of hypofibrinogenemia rather than dysfibrinogenemia. Fibrinolysis did not account for the reduced fibrinogen level. This case demonstrates that congenital low fibrinogen levels may be associated with placental abruption and that an abnormal fibrinogen molecule is not necessary.