Yellow Jaundice (Hyperbilirubinemia)

About half of newborn babies get some yellow jaundice and their skin turns yellow. They aren't born with it — it develops when they are two or three days old.

Why do newborns get yellow jaundice?

The yellow color comes from a chemical called bilirubin. We all make bilirubin all the time. It comes from our red blood cells when they get old and die. An average red blood cell lasts about 120 days, then most of it gets recycled, except for a deep yellow chemical, bilirubin.

Blood Cells

Our liver takes the bilirubin out of our blood stream and puts it into our digestive system in the form of bile. Bile gets its greenish-yellow color from bilirubin. If our liver is working, we don't walk around with yellow skin.

For your baby, when he is inside mom, mom's liver and placenta are taking care of all of his body's functions, including the bilirubin. So, when the baby is born, and the cord is cut, there's no more help from mom's body or the placenta. The baby's body has to start doing everything independently.

The process of the liver turning on isn't like flicking a light switch. It's a complex biochemical process. It can take a few days to a week for a normal baby's liver to "turn on" and start taking care of the bilirubin.

During that time, red blood cells are still being recycled and bilirubin is being produced. So, the baby turns yellow.


Why do we worry about yellow jaundice in newborns?

Other body functions don't turn on right away. One body function that is of concern is the protective "blood–brain barrier." We all have a blood–brain barrier. It wraps around every blood vessel in our brain. It acts as insulation, protecting the brain from toxic chemicals.

It takes a few days to a week for a newborn's blood–brain barrier to start working to filter out bad chemicals. During this time, the baby's brain could be exposed to high levels of bilirubin. If a young enough brain is soaked in a high enough level of bilirubin long enough, permanent brain damage can result.

We don't want any baby's brain to possibly get exposed to a level of bilirubin that could possibly cause brain damage. We are very conservative when it comes to newborn babies.


When does yellow jaundice need to be treated?

One of the jobs of the American Academy of Pediatrics (AAP) is to assemble national experts to make decisions and recommendations about diagnosing and treating diseases in infants and children. Most pediatricians follow the national guidelines set by the AAP Committee on the Care of the Fetus and Newborn concerning the diagnosis and treatment of infant hyperbilirubinemia. Here is a graph that we use:


The level of bilirubin in the blood at which we start treatment depends on the gestational age of the baby, the baby's age in hours, the blood type of the mom and the baby, and several other factors. Each day, a higher level of bilirubin is tolerated. For most babies, the treatment can be stopped or modified within two or three days.


Why are some babies more susceptible to yellow jaundice than others?

Not all babies get yellow jaundice. Yellow jaundice is more likely in the following cases:

  • If a baby is born early, after less than 38 weeks gestation, her liver is less mature and takes longer to "turn on." Premature babies almost always need treatment for yellow jaundice.
  • If a baby is slow to start feeding, the liver may take longer to "turn on." The milk going through the baby's digestive system is one of the signals that prompts the baby's liver to start working. If your baby needs treatment for yellow jaundice, you may be asked to supplement your breast milk with formula or pumped milk until he is nursing well.
  • If there is a difference between mom's blood type and baby's blood type, the baby's red blood cells may be breaking down faster than normal and more bilirubin is being produced.
  • If a large bruise formed during labor, that bruise contains red blood cells that are breaking down, forming more bilirubin for the baby's liver to handle.
  • If the baby is sick with something else, like an infection, that puts more stress on his body and decreases his ability to adapt to being born.

In each of these cases, we will start treatment earlier than we would in a normal term baby.


How is yellow jaundice treated?


If your baby's bilirubin level is high, he will be started on phototherapy (light treatment). The blue wave length of natural light is absorbed by the bilirubin chemical in his skin when it is exposed to the light. The light wave changes the shape of the bilirubin molecules (the process is called photo-isomerization). This different–shaped bilirubin molecule is more easily taken out of the baby's body by his kidneys. His urine will turn a dark, dusty color during phototherapy.

The light treatment is safe and effective. We cover the baby's eyes for comfort. We know that if we stare at that bright blue light long enough we get a headache. The light is not dangerous to his eyes, or ours. Also, babies under phototherapy treatment need to sleep, and they seem to sleep better if their eyes are covered.


The more a baby's skin is exposed to the blue light, the better it works. The light treatment does not work through clothes or diapers. After a few hours of light exposure, you can tell that the yellow is disappearing from his skin, but is still there under the diaper and the eye-shades.

The light therapy isn't "turning on" the baby's liver. Time and feeding will do that. However, it buys time, keeping the bilirubin at a safe level until the baby's liver turns on and starts taking care of the bilirubin on its own.

Feeding your baby is an essential part of treating yellow jaundice. Milk going through your baby's digestive system is the signal to his liver that tells it to turn on. So, your baby must be taken out from under the phototherapy lights to get a good feeding at least every three hours. If your milk hasn't come in yet, and the baby needs phototherapy, you may be asked to supplement your baby's feedings with your pumped milk or formula until the baby is nursing well at the breast.

At our hospital, we attempt to follow a schedule of three hours under the lights, followed by 1/2 hour of feeding, three hours under the lights, 1/2 hour of feeding, repeat ... Of course, newborn babies don't often follow adult schedules, but that is the plan.


If the baby isn't under the lights, the bilirubin keeps going up. If the baby doesn't get fed, the liver isn't turning on. So there must be a balance between the two important parts of treatment — phototherapy and feedings.

If your baby's bilirubin level is not too high, you may be offered home phototherapy treatment. The advantage of home phototherapy is that you are at home! Phototherapy is safe. There is no way you can harm your baby with phototherapy. The disadvantage of home phototherapy is that the light generating equipment is not as powerful as the equipment that is used in the hospital. The home equipment works, but, it can take days longer for the bilirubin level to get low enough to stop treatment.


Do sunny windows really help?

Yes, they do. Natural sunlight contains all the wavelengths of light, so it has plenty of the blue wavelength that converts the bilirubin molecule into the easier-to-pee-out form.

sunny window

But it must be light THROUGH A WINDOW, not outside. The window glass filters out the UV light that causes sunburn. We do not want sunburned babies!

Two or three times a day, fifteen to twenty minutes at a time of bright sunlight shining on your baby's bare-naked skin really will help keep yellow jaundice down. It sort of depends on what kind of windows you have at your home. Babies usually like the warmth and stretch out like a cat. I tell parents fifteen to twenty minutes because we don't want the baby too hot because of the sunlight, or too cold because his clothes are off.


How do we decide to stop treatment for yellow jaundice?

We decide to stop the phototherapy the same way we decide to start it — by measuring the amount of bilirubin in your baby's blood and comparing it to the safe levels for your baby's age and risk factors.

Usually the baby's blood level is checked every day or so. On average, term babies get phototherapy for two or three days, longer if they are treated with phototherapy at home (because the lights used at home are not as strong as the lights used at the hospital). The longest I ever treated a baby with phototherapy was two weeks, but that was quite unusual.

Once the bilirubin level starts going down without phototherapy, we know the liver is starting to work. In newborn babies, yellow jaundice is not even a disease, but an immaturity of the baby's liver. The problem goes away. If you think of treating yellow jaundice as preventive medicine, then you have the right understanding.


Thanks to Janelle Aby MD, Stanford School Of Medicine, Newborn Nursery, and Lucille Packard Children's Hospital for the use of occasional photographs.