Tricuspid atresia is a heart condition where the tricuspid valve doesn’t develop properly. This prevents blood from flowing from the right atrium to the right ventricle. Instead, blood is forced through an atrial septal defect from the right atrium to the left atrium and left side of the heart. The right ventricle, which normally pumps blood to the lungs, is often underdeveloped and very small (hypoplastic). This makes it difficult for blood to reach the lungs to pick up oxygen. A ventricular septal defect is often present. There can be other differences in the heart that can occur with tricuspid atresia. Your medical team will let you know if there are any other differences that your baby’s heart may have.