“Blue baby” congenital defects are heart abnormalities that cause too little oxygenated blood to reach the systemic circulation, producing central cyanosis — a bluish colour of the lips, tongue and skin.
This usually happens because deoxygenated blood bypasses the lungs, pulmonary blood flow is severely restricted, or oxygenated and deoxygenated blood mix abnormally before reaching the body.
Examples include Tetralogy of Fallot, Transposition of the Great Arteries, pulmonary or tricuspid atresia, TAPVR, Truncus Arteriosus, DORV and severe Ebstein Anomaly.
The term is useful as a simple physiological description, but it is not a diagnosis in itself: the exact cause of cyanosis depends on the underlying anatomy and direction of blood flow.
