Jaundice is the name for the yellowish color of the skin and eyes that may develop in newborn babies. It occurs because bilirubin, which is a substance produced by the normal breakdown of older red blood cells, is not able to be cleared by the newborn baby's liver. The bilirubin builds up, giving the skin a yellow-orange hue. Treatment often involves phototherapy, which means the baby is placed under ultraviolet light; the UV light helps with bilirubin breakdown. There are several possible causes of jaundice in a baby.
Physiologic ("Normal") Jaundice
Normal jaundice occurs when the baby's liver is simply not able to keep up with the rate of blood cell breakdown. When this occurs, one of the byproducts of this breakdown, bilirubin, accumulates in the blood. This is called hyperbilirubinemia, and often appears on the second or third day of a newborn baby's life. According to a study published in the medical journal the New England Journal of Medicine, most newborns will have a mild increase in their bilirubin levels. As the levels of bilirubin increase, the characteristic yellowish skin appears; the whites of the eyes, called the sclera, may also turn yellow. According to DRs. Wong and Bhutani, writing in the medical database UpToDate, physiologic jaundice will often resolve within the first one to two weeks of the baby's life.
Jaundice Due to Increased Bilirubin Production
According to the Mayo Clinic web page "Infant Jaundice," other, underlying causes may be the root cause of a baby's jaundice. The most common cause of jaundice that is not simply "normal" jaundice is an abnormal increase in production of bilirubin. This may be due to one of several conditions that cause an increase in red blood cell breakdown, which leads to an increase in bilirubin production and thus the high levels in the blood called hyperbilirubinemia. One condition that results in too much bilirubin is an incompatibility between the immune system of the mother and the immune system of the baby within the mother's womb. This is called isoimmune-mediated hemolysis.
Another potential reason for increased bilirubin production is due to diseases of the red blood cells; these are often inherited and include a disease called hereditary spherocytosis, in which the blood cells are abnormal in shape and break much more easily than usual. Finally sepsis--the spread of bacteria, viruses, other disease-causing organisms, or toxins throughout the baby's body--may also lead to increased production of bilirubin. According to the medical textbook "Neonatal-Perinatal Medicine," the reason for this is unclear but it is theorized that the stress on the baby's body also increases the fragility of the cells--including the blood cells--and leads to jaundice.
Jaundice Due to Decreased Bilirubin Clearance
Several genetic diseases may cause the baby to have a decreased ability to clear the bilirubin from her body. The most common inherited disorder related to bilirubin is called Gilbert's syndrome. In this disease, a mutation in a certain gene leads to a decrease in the production of an enzyme called UGT. The lower levels of UGT result in less bilirubin being cleared from the baby's body, resulting in hyperbilirubinemia and jaundice in the baby. Another potential inherited disease is called Crigler-Najjar syndrome: in type I of this syndrome, the baby is born with no detectable UGT and develops extremely severe hyperbilirubinemia. In these cases, lifelong phototherapy is needed in order to prevent neurological complications that occur when the bilirubin crosses from the bloodstream into the brain and actually attaches to the brain tissue. In Crigler-Najjar type II, the baby has a small amount of UGT enzyme, but it is not enough to prevent hyperbilirubinemia. In such cases, treatment with the medication phenobarbital may be helpful.
Jaundice Due to Increased Circulation of Bilirubin
A common cause of jaundice that is related to increasd circulation within the baby's bloodstream is called "breastmilk jaundice": this is defined as physiologic jaundice that does not resolve within the first week of life. According to Drs. Wong and Bhutani writing in UpToDate, such jaundice usually resolves without treatment within the first three months of the baby's life. However, it should be monitored to make sure that levels of bilirubin are not reaching dangerous levels. The cause of breastmilk jaundice is unclear; a 1986 study published in the medical journal Lancet theorized that an unknown substance within breastmilk may cause increased absorption of bilirubin, leading to the increased levels of bilirubin in the baby's blood. Another potential cause of increased bilirubin circulation leading to jaundice in a baby is an obstruction within the intestine; this is more frequent with small intestine obstructions than with large intestine obstruction.
References
- "New England Journal of Medicine"; Neonatal hyperbilirubinemia; P.A. Dennery et. al.; February 2001
- "Neonatal-Perinatal Medicine: Diseases of the Fetus and Infant"; A.A. Fanaroff et. al.; 2006
- "Lancet"; beta-Glucuronidase and hyperbilirubinaemia in breast-fed and formula-fed babies; G.R. Gourley and R.A. Arend; March 1986
- "UpToDate"; Denise S. Basow; 2010
- Mayo Clinic: Infant Jaundice
