Jaundice becomes dangerous when bilirubin levels exceed 20 to 25 milligrams per deciliter. High bilirubin levels, which indicate severe jaundice, can cause extreme sleepiness, seizures, muscle rigidity and intellectual disability, according to MedlinePlus.
As the body destroys old red blood cells, it creates bilirubin. Excess amounts of this pigment cause the skin to look yellow, a condition known as jaundice. High levels of bilirubin can collect in the brain tissue and cause complications such as hearing loss and brain damage. Depending on the stage of the condition, high levels of bilirubin in newborns manifest in poor feeding or sucking habits, arched back and movement disorders. Newborns in the late stages of kernicterus, a condition characterized by extremely high levels of bilirubin, can die, as stated by MedlinePlus.
Most newborns have physiological jaundice that is noticeable within two to four days of birth. The condition is typically harmless and usually dissipates within two weeks. Severe jaundice may occur if a baby has a blood type mismatch with its mother, lacks certain enzymes, or has infections or abnormal blood cell shapes. Genetic disorders, certain medicines, low oxygen and disorders of the liver may also precipitate dangerous levels of jaundice, according to MedlinePlus.