Jaundice in newborns , which produces a yellow color to the skin and eyes, is caused by a buildup of bilirubin in the blood (hyperbilirubinemia). In the womb, a fetus obtains nutrients and eliminates by-products, such as bilirubin, through the umbilical cord. After birth, the baby's organs take over these jobs.

Newborns may develop jaundice from a buildup of bilirubin for slightly different reasons.

Physiologic jaundice

Physiologic jaundice develops between 1 and 5 days after birth because babies' organs are not yet able to get rid of excess bilirubin effectively. Whether jaundice is noticeable depends in part on how high blood bilirubin levels reach.

If noticeable, the yellowing of the skin and eyes usually appears about 24 hours after birth and increases until about the third or fourth day. Most often, bilirubin levels in the blood then gradually lower and the yellowing fades or disappears in about a week without causing problems.

Premature babies, whose organs often are not fully developed, are less able to eliminate bilirubin effectively and are more likely than full-term babies to develop noticeable yellowing related to jaundice.

Breast-feeding jaundice

Breast-feeding jaundice is caused by mild dehydration, which prolongs and intensifies physiologic jaundice. When your baby doesn't get enough fluids, it makes it even harder for your baby's growing body to get rid of bilirubin.

A baby is less likely to develop significant breast-feeding jaundice if he or she gets enough to eat. The American Academy of Pediatrics recommends that mothers breast-feed about 8 to 12 times every 24 hours.¹ If jaundice is noticeable, it may help to feed your baby every 2 hours.

Frequent feedings increase the production of colostrum (and breast milk, once it comes in), which ensures that the baby gets enough nutrition and fluid to get rid of the extra bilirubin. Supplementing breast milk with water or sugar water does not help lower the bilirubin levels in these babies.

Breast milk jaundice

After physiological or breast-feeding jaundice or the two combined has resolved (usually by 5 to 7 days), bilirubin levels may rise again during the second week (10 to 14 days) in breast-fed babies. This type of jaundice is likely related to how certain components of breast milk affect bilirubin elimination in the infant.

Usually, breast milk jaundice gradually decreases, although most babies often have mild jaundice throughout the duration of breast-feeding. Bilirubin levels rarely rise to harmful levels, and most often health professionals recommend continuing with exclusive breast-feeding. Sometimes a bilirubin blood test is done to assure that the bilirubin level is in an acceptable range.

Most of the time bilirubin does not cause problems, but occasionally the amount of bilirubin in a newborn's blood rises to a level that could be harmful. When this happens, the yellowing of a baby's skin and eyes (jaundice) becomes more pronounced and he or she may become irritable and sluggish and have a high-pitched cry. Parents should report these symptoms to their doctor right away.

Rarely, excessive amounts of bilirubin build up in the blood and lead to brain damage (kernicterus), which can result in hearing loss, intellectual disability, and other problems.