The patient was a 38-year-old Japanese woman who had been diagnosed with hereditary angioedema type I at 7 years of age based on her family history. She had undergone four pregnancies. She gave birth to a healthy baby girl after her first pregnancy and had reported few episodes of angioedema. However, she subsequently required abortions due to frequent angioedema episodes that occurred during her three subsequent pregnancies. Thus, our patient showed two clinical pregnancy courses. After treating her with C1-inhibitor concentrate, her symptoms of angioedema disappeared. The preventive use of C1 inhibitor concentrates should be considered in hereditary angioedema (HAE) patients with frequent angioedema attacks during pregnancy.