Introduction
Neonatal jaundice – also called neonatal icterus or Icterus neonatorum (ancient Greek ikteros = jaundice) – describes the appearance of yellowing of the skin and sclera of the eyes (“sclerae”) of newborns. This yellow coloration is caused by deposits of the decomposition products of the red blood pigment (hemoglobin). The degradation product responsible for this is called bilirubin.
Jaundice in the first days of life is usually a physiological, harmless process that occurs in about 60% of newborns. It is an expression of the replacement of the red blood pigment (hemoglobin) from the fetus by the adult (“adult”) pigment of the newborn. A neonatal jaundice that persists for more than two weeks after birth is called jaundice prolongatus. The jaundice often reaches its full extent around the 5th day of life, after which it usually heals on its own and without consequences. Only rarely do such high concentrations of bilirubin occur that threatening complications can arise (“kernicterus” or “bilirubin encephalopathy”).
Causes
Newborn jaundice can have a variety of causes, but first of all a distinction must be made between physiological, harmless jaundice and jaundice due to congenital or acquired metabolic disorders in bilirubin breakdown. The physiological, harmless neonatal jaundice is caused by an increased breakdown of the prenatal red blood pigment (fetal hemoglobin), which is replaced by adult (adult) hemoglobin after birth. However, because the enzymes responsible for this in the liver are still immature and not fully active, the bilirubin cannot be broken down as quickly as it is produced and is deposited in the skin and sclerae.
Newborn jaundice due to disturbances in the bilirubin metabolism or an excess of red blood pigment outside the normal hemoglobin conversion after birth can in turn have numerous causes. These include, for example, bruising that has occurred in the newborn during birth and has to be removed, bile stasis due to congenital constriction or obstruction of the bile duct, inflammation of the liver (hepatitis) or blood cell decay (hemolysis) due to blood group incompatibility between the child’s and mother’s blood group during pregnancy (“rhesus factor incompatibility” or Morbus haemolyticus neonatorum). In addition, prolonged neonatal jaundice can be a sign of congenital hypothyroidism or neonatal infection.