Jaundice About 60% of newborn infants in the United States are jaundiced, that is they look yellow. Jaundice is the yellow coloring of the skin and other tissues. Jaundice can often be seen well in the sclera, the "whites" of the eyes, which look yellow. Many babies look jaundiced (60%), but they are not deeply jaundiced, not jaundiced below the abdomen, and they act OK - they nurse, they aren't too sleepy, they have normal muscle tone, their cry is normal, they don't arch their backs.
Kernicterus Kernicterus is a form of brain damage caused by excessive jaundice. The substance which causes jaundice, bilirubin, is so high that it can move out of the blood into brain tissue. When babies begin to be affected by excessive jaundice, when they begin to have brain damage, they become excessively lethargic. They are too sleepy, and they are difficult to arouse - either they don't wake up from sleep easily like a normal baby, or they don't wake up fully, or they can't be kept awake. They have a high-pitched cry, and decreased muscle tone, becoming hypotonic or floppy) with episodes of increased muscle tone (hypertonic) and arching of the head and back backwards. As the damage continues, they may develop fever, may arch their heads back into a very contorted position known as opisthotonus or retrocollis.