Yellow Babies, Blue Lights: an intro to jaundice

Jaundice is a common problem in newborns–one that is responsible for a lot of office visits and hospitalizations in the first few days after birth. But even though jaundice (or hyperbilirubinemia) is very common, most parents don’t understand what causes it or why doctors care so much about it. So in case you’re wondering what the fuss is all about, here’s what you need to know.

When we say a baby is “jaundiced,” we mean that his skin is yellow, which is the result of having high levels of a molecule called bilirubin in the body. Bilirubin is a waste product formed when red blood cells are recycled–a process that happens continuously in all of our bodies. Under most circumstances, bilirubin is processed in the liver into a form that can be eliminated in the stool and urine. But prior to birth, bilirubin simply crosses over the placenta into the mother’s bloodstream, to be processed by her liver. And after a baby is born, there are several potential reasons that this process may not work as it should.

The most common reason is physiologic (or normal) jaundice. Because the baby’s liver has never had to process bilirubin, the enzyme responsible for this task isn’t very active. After birth, it can take a few days for the liver to adjust, and the bilirubin level rises temporarily until the liver can catch up. This is a normal process that occurs in all infants, to varying degrees, and it isn’t harmful at all.

Another very common issue is breastfeeding jaundice, or what might be better known as not-feeding jaundice. When an infant is born, it may take up to a few days for the mother’s milk to come in. And because bilirubin is eliminated in the stool and urine, the more an infant eats, the faster it goes away. This problem is uncommon in formula-fed infants simply because there’s no delay after birth before the milk is available. But if you were to restrict an infant’s access to formula for the first few days (not something I’d recommend), we’d see the same result.

Another potential issue with breastfed infants is breast milk jaundice. (Sorry, I didn’t choose the frustratingly similar names.) We think this is due to a substance in breast milk that causes the baby to reabsorb some of the already-processed bilirubin from the intestine. Breast milk jaundice is seen only in breastfed infants. It can last weeks, but it does not reach harmful levels and is not a reason to stop breastfeeding.

In some cases, there is a problem with the compatibility between the mother’s and infant’s blood types. There is a possibility that the mother could make antibodies that attack the baby’s red blood cells because of differences in the A/B/O or Rh (+ or -) antigens on their blood cells. These antibodies can travel across the placenta, and then cause rapid breakdown of the baby’s red blood cells, called hemolytic disease of the newborn. This can get pretty complicated, but it typically has potential to affect infants of mothers with the following blood types: A-, B-, AB-, O+, or O-. In these cases–or at some hospitals, for all infants–we check for these antibodies and watch the baby’s blood counts and bilirubin more closely because of the increased risk for jaundice.

And then there are lots of other reasons for jaundice, which can range from mild to severe:

  • There are genetic differences in how effectively bilirubin is processed.
  • Some people have red blood cells that break down faster, so the liver has more work to do.
  • Premature or very sick infants often have significant problems with jaundice.
  • Obstruction in the liver can prevent the processed bilirubin from being transferred to the intestine.

The reason we care about jaundice is that, just like bilirubin is deposited in the skin, it is deposited in other tissues as well–most notably, the brain. At very high levels, this can cause a condition called kernicterus, which results in severe and permanent brain damage or death. Scary, right? But it’s also extremely rare in the developed world, and it’s almost always preventable just by monitoring bilirubin levels in babies and treating those that start to approach dangerous levels.

Not too many years ago, pediatricians would try to estimate an infant’s bilirubin by how yellow she looked or how much of her body appeared jaundiced. But that’s not easy, given the varying skin tones in our patients and differences in our color perception. Eventually, we figured out we’re just not very good at it. So now, we check a bilirubin level in all infants before they go home from the hospital. This can be done as a blood test taken from a heel stick, or using an instrument that analyzes the color of the baby’s skin (but still requires a blood test if the level is high).

Because we know that an infant’s bilirubin level will go up over the first few days, there’s no set number that is “bad.” We take into account the infant’s age in hours, gestational age, and several risk factors to decide if (and how soon) we need to recheck the level, or if we need to take steps to bring the level down. For many infants, checking this bilirubin once may be enough. Others require frequent monitoring over the first few days until the level stops rising. And it’s not uncommon for us to need to take steps to bring the level down before it becomes potentially dangerous.

For breastfeeding infants, appropriate lactation support and frequent nursing helps to minimize any problems. In some cases, it’s necessary to supplement with formula while the mother and infant continue to work on breastfeeding. (As wonderful as breastfeeding is, Rule #1 is: “Feed the baby.”)

When that isn’t enough, our next step is phototherapy. For the true geeks among you, this is a light that emits photons of a specific wavelength (around 450 nanometers), resulting in photoisomerization of subcutaneous bilirubin molecules into one of two hydrophilic forms, allowing them to be excreted in the absence of hepatic conjugation.

For everyone else, it’s a blue light that makes jaundice better.

There are several forms of phototherapy available. Depending on the severity of the jaundice, this may be a glowing blanket that parents can wrap around their baby at home, or a crib with multiple lights bright enough to see through the hospital door (not really, but they’re bright). And in the very rare cases in which the level is extremely high, or isn’t responding adequately to phototherapy, we have a few other tools that we can use as well.

The good news is that, while frequent bilirubin checks or a brief hospitalization can be inconvenient, it is extremely uncommon for infants to have any long-term problems from jaundice. Checking for jaundice is part of our routine newborn care, and a topic that you should feel comfortable discussing with your pediatrician.


Hopefully, I’ve helped to demystify this poorly-understood topic and to allow you to be an informed participant in your child’s medical care. As always, I appreciate you reading and sharing my blog posts, and I welcome any questions or comments you may have. If you’d like to follow me on social media, it’s not hard to find me on Facebook or Twitter. -Chad