Brain embolisms in younger persons are rare but are often caused by a paradoxical embolism, the embolic entry of a venous thrombus into the systemic circulation through a right-to-left shunt. A 27-year-old pregnant woman presented with hemiplegia that had been treated with an antiplatelet agent since the occurrence of a paradoxical brain embolism via the pulmonary arteriovenous fistula. A tendency of hypercoagulation is generally observed during pregnancy, so a patient with this condition has a strong risk factor for venous thromboembolism during pregnancy and even more so for arterial thromboembolism under the intense strain of labor, which is much stronger than that of the Valsalva maneuver. This case had been controlled well with an antiplatelet agent and an anticoagulant while the levels of coagulation and fibrinolytic factors were monitored and was followed by a successful pregnancy outcome.