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Hyperbilirubinemia, also called jaundice (or sometimes “yellow jaundice”), is one of the most common conditions experienced in newborn babies. Virtually all babies develop some degree of hyperbilirubinemia. In fact, many factors present only in newborns promote hyperbilirubinemia and many experts believe it’s a good and natural occurrence. However , like so many things, whereas a little bilirubin may be beneficial, too much bilirubin in the blood can be dangerous to the newborn infant and must be treated.

The word “hyperbilirubinemia” literally means “too much bilirubin in the blood.” (Hyper = too much; emia = in the blood.) Bilirubin is a molecule released into the bloodstream when red blood cells break apart. In older infants, children and adults, the liver processes this molecule and sends it into the intestines where it is eliminated in the stool. The molecule is yellow, and is responsible for the characteristic yellow color of baby poop. Specifically in newborn infants, in the first few days after birth a disproportionately large number of red blood cells are breaking apart, and the liver is not yet very good at processing the bilirubin. The baby may not be eating very much, and not pooping frequently. The result of high production and low elimination is a backup of bilirubin in the blood – hyperbilirubinemia.

There are lots of things about hyperbilirubinemia that we know, and lots of things we don’t know. For example, we know that if you squirt bilirubin into a petri dish with brain cells in it, the brain cells will die. We know that babies who have experienced extremely high levels of bilirubin in the blood can have a characteristic and permanent collection of brain abnormalities, called bilirubin encephalopathy. But we also know that some babies have these same high levels of bilirubin in their blood and remain perfectly normal (and some who never had high levels develop the same encephalopathy!) So, the most obvious question is…

How High is Too High? The short answer is…we don’t know. And because we don’t know, you may see many different responses by your health care team to your baby’s hyperbilirubinemia.

Hyperbilirubinemia is treatable – bilirubin encephalopathy is not. When, how, and for how long your baby’s hyperbilirubinemia is treated depends on many factors. Your neonatologist (or pediatrician) may consider the following:

  • Your baby’s gestational age at birth (term, late preterm, preterm) – We believe that the preterm baby’s brain is more vulnerable to the toxic effects of bilirubin. Furthermore, the preterm infant’s liver takes longer to begin processing bilirubin, which leads to higher levels for longer times than in term infants.
  • Is s/he otherwise healthy, or is s/he sick and/or in the NICU? – Bilirubin damages the brain by crossing the blood-brain barrier, and more bilirubin can get across it when the baby is sick and/or has a higher level of acid in his/her bloodstream than usual.
  • Is there an abnormality in your baby’s blood that is causing more of it than typical to breakdown (so called hemolytic hyperbilirubinemia – see more on this below)?
  • Is your baby feeding vigorously and with breastmilk or with formula? – Breastmilk contains factors that actually work to undo what the liver does to help eliminate bilirubin, which suggests that Nature intended the newborn infant to experience some degree of elevated bilirubin levels.


Bilirubin is easily measured in the blood from a small sample sent to a hospital laboratory. How your doctor responds to the result is more difficult to predict. The choices include: 1) getting another level in a day or two; 2) starting phototherapy at home; 3) admitting your baby to the hospital for treatment; 4) do nothing. In 2004 The American Academy of Pediatrics published a clinical guideline with recommendations for monitoring and treating hyperbilirubinemia in babies born at equal to or greater than 35 weeks estimated gestational age (EGA). See Babies born at less than 35 weeks EGA are most likely in the hospital for the first few days/weeks of life and treatment decisions will be made by the attending physician based on clinical judgment.


The most common treatment for hyperbilirubinemia is phototherapy. Light waves of a very specific frequency work to convert the bilirubin in your baby’s skin (which is what makes him/her appear yellow) to a different form, which s/he can eliminate much more easily than the original form. The light waves must touch the baby’s bare skin, so s/he must be as fully exposed as possible under the lights. The light waves are in the blue-green spectrum, which is why the lights appear that odd color. They are not in the ultraviolet spectrum, so do not “tan” or sunburn your baby, and they are not in the infrared spectrum, so they are not hot. How well they work depends on: 1) how much skin surface area is exposed; 2) for how long; 3) and how strong the lights are (which can – and should – be measured regularly by the nurse).

Some physicians may tell you to stop feeding your baby – especially if you are breastfeeding. Although this historically was a common practice, research studies have shown that the hyperbilirubinemia resolves quicker if the baby continues to feed, either at breast or on formula at the mother’s choice. While your doctor may not want you to take your baby out from under the lights to feed, it is not necessary to stop feeding breastmilk to your infant. While s/he is being treated, you can pump and bottle feed your expressed breastmilk to your baby under the lights without disrupting treatment.

If your baby’s bilirubin level does not respond to phototherapy (or in other very rare circumstances), your neonatologist may order an exchange transfusion, which is the ultimate treatment. Exchange transfusion used to be much more common than it is today, but it still remains the definitive treatment when the bilirubin is dangerously high and not responding to phototherapy. An exchange transfusion involves actually removing your baby’s high-bilirubin blood and replacing it with new blood from the blood bank that does not have high levels of bilirubin in it. This is done slowly, over a period of several hours. Briefly, a small amount of your baby’s blood is removed through an intravenous line placed in a large vein or artery and the same amount of new blood is pushed in through a different intravenous line. This process occurs repeatedly, until twice the estimated total blood volume in your baby has been removed and replaced. As you can imagine, the procedure is risky, and you must give permission before it will be performed. Be sure to ask all of your questions about how it will be done, who will do it, and know the risks and benefits before signing the consent form.

All babies are born with extra red blood cells, intended to carry them through until their own bodies start making them. Some babies, like those born to smokers, those whose mothers lived at altitude during the pregnancy, mothers with high blood pressure or diabetes during the pregnancy, have even more red blood cells than normal, leaving more to break down after birth. Sometimes, additional conditions or abnormalities result in red blood cells breaking down even faster – which can lead to particularly early and high levels of hyperbilirubinemia.

  • Blood group incompatability – Red blood cells have proteins on their surfaces called antigens, and these antigens have names. The most common ones – A and B -- result in your blood type; you can be Blood Type A, Blood Type B, or Blood Type AB. If you have neither A nor B on your red blood cells, you have Blood Type O. Another antigen, known as the D antigen, is either there, or it’s not. If you have the D antigen, your blood type is Positive, and if you don’t, your blood type is Negative. The most common blood type is O+ and the rarest AB­.

Your body makes antibodies to foreign invaders, which are distinguished from your own cells bythe antigens on the foreign invader. When a foreign antigen is detected, the antibody that corresponds to that antigen attaches itself to the antigen and destroys the cell. This is how your body protects you. And, when you’re pregnant, these antibodies pass across the placenta into your baby to protect him/her also. If your baby’s blood has an antigen on it that your blood doesn’t (so your blood type is O and/or “negative”), antibodies made by your body to protect you cross into your baby, see your baby’s blood antigen, think this is a foreign invader, and attach to your baby’s red blood cells to break them apart. This increases the amount of bilirubin spilled into your baby’s blood stream, leading to higher levels of bilirubin much earlier than usual. This condition is potentially dangerous to your baby and must be monitored very closely.

  • Inherited blood cell defects – Some rare types of inherited red blood cell abnormalities can also cause your baby’s red blood cells to break down faster and in greater numbers than usual, leading to hyperbilirubinemia. Two main categories of abnormalities are: 1) enzyme defects; and 2) membrane defects. Enzyme defects, such as G-6-PD deficiency, occur more often in certain ethnic groups. Membrane defects, such as spherocytosis, result in red blood cells that are abnormally shaped. Because these types of abnormalities are inherited, there may be a family history of anemia or hyperbilirubinemia.

Breastmilk Jaundice.

As mentioned above, there are many factors present only in the newborn baby that actually work to create and preserve elevated levels of bilirubin in the blood. This observation has led many experts to believe that some degree of hyperbilirubinemia is actually a good thing. It is known that substances in breastmilk help to potentiate this hyperbilirubinemia. Some women’s milk has even more of these substances than usual such that their babies stay visibly jaundiced for longer period of time – sometimes up to several months. This is called “breastmilk jaundice.” While it is a totally normal condition, tests must be performed to be certain. Breastfeeding should not be stopped because of breastmilk jaundice.

For the vast majority of babies – both premature and term – their hyperbilirubinemia is not the result on any lifelong abnormality and will resolve quickly without any residual after-effect, never to return again. If you have questions, be sure to ask your neonatologist or pediatrician.

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