Thanks for posting your query at HealthCareMagic. Transposition of the great vessels is a condition where the aorta or the artery which is supposed to carry oxygenated blood to the systemic circulation, arises from the right ventricle which pumps deoxygenated blood that is intended to go to the lungs. In dextro-Transposition of the great arteries (dextro-TGA) is a cyanotic congenital heart defect where deoxygenated blood from the right heart is pumped immediately through the aorta and circulated to the body and the heart itself, bypassing the lungs altogether, while the left heart pumps oxygenated blood continuously back into the lungs through the pulmonary artery. This condition would have been physiologically non-viable if the ductus arteriosus which is a connection between the right and left circulation does not remain open. In normal situation it closes soon after birth. Levo-Transposition of the great arteries is an acyanotic heart defect in which the primary arteries are transposed, with the aorta anterior and to the left of the pulmonary artery, and the morphological left and right ventricles are also transposed. I hope that I have been able to explain the normal physiology in the two variants. I do not know which variant your baby has. Feel free to communicate back in case of further queries.