Interrupted aortic arch (IAA) is fatal if not diagnosed. Prenatal diagnosis is helpful, but it is difficult to detect IAA and even more so to differentiate types A and B prenatally. Our objectives were to find a way to detect IAA using 2 views-three-vessel view (3VV) and four-chamber view (4CV)-and to differentiate between types A and B. We retrospectively analyzed fetal echocardiographic images and medical records of eight IAA patients. All eight patients had a ventricular septal defect (VSD) on 4CV. The aorta/main pulmonary artery (Ao/MPA) diameter ratio on 3VV was significantly low, which is characteristic of type B IAA. The left/right ventricular diameter (LV/RV) ratio on 4CV was 0.61± 0.17 for type A and almost 1.0 for type B. The thymus was not observed on 3VV in some type B IAA patients. These findings suggest that we could increase the number of prenatal diagnoses of IAA using the Ao/MPA ratio on 3VV and the presence of VSD on 4CV. Additionally, we could differentiate types A and B with the LV/RV ratio on 4CV, the Ao/MPA ratio, and the presence of a thymus on 3VV, which results in better management of IAA after birth.