Jaundice in the newborn baby is a complex topic. It is very common for babies to develop some jaundice during the first week of life and, in some cases it is normal for this to persist for a few weeks. The first step in understanding jaundice is to understand what actually causes the yellow discoloration of the skin and eyes that we see in jaundice.
The actual compound that causes jaundice is called bilirubin. Bilirubin is produced when red blood cells are broken down. It is normally processed in the liver and excreted through the bile duct into the gut and out of the body in the stool long before it ever reaches a high enough level to cause yellowing of the skin. In adults and children, jaundice is not normal and often means something is going wrong with the liver.
In babies, however, it is perfectly normal to have a brief period of high bilirubin (relatively high… but we will get to this in a moment). Babies have shorter lived red blood cells which means more of them are getting broken down. Babies also have an immature liver, especially premie babies, and the bilirubin cannot be processed fast enough. With more being produced and less being processed, it starts to build up in the blood stream and body tissues, like the skin and eyes, leading to the characteristic yellow color of jaundice.
This state is usually transient and resolves without any problems over the first week of life. It usually peaks at 2 to 4 days of life. After being processed in the liver, bilirubin is excreted into the gut through the bile duct and passes out of the body in the stool so adequate feeding during these first few days is helpful in getting rid of jaundice. The other way our bodies break down bilirubin is through the skin. UV light of a particular wavelength can help decrease bilirubin levels.
Why do we measure bilirubin levels in babies?
If this is a normal state for babies, why do we care so much about jaundice? Why do pediatricians check bilirubin levels so frequently, use phototherapy lights and make such a big deal about it?
Doctors use a measuring stick called the Bhutani nomogram. This graph plots out normal levels of bilirubin based on a newborn’s age in hours. As we said before, bilirubin is at a pretty negligible level in a healthy adult but in newborns we expect some. How much is too much? The simple answer to this is that a level of about 25 mg/dL is pretty concerning because, above this level, bilirubin can be neurotoxic and effect a baby’s brain development. Kernicterus is the name given to the long term neurologic deficits seen when bilirubin levels get too high in the newborn period. Avoiding this state is of the utmost importance.
If all babies get some elevated bilirubin, how do we know which ones will get too high and which just have a ‘normal’ amount of bilirubin? This is where the Bhutani nomogram comes in. It shows us the expected level of bilirubin in a newborn of a particular age. A bilirubin of 14 in a 5 day old is not concerning in and of itself, while it would be in a baby only 24 hours old. Doctors use the curve of expected levels to determine which babies seem to have a bilirubin that is rising too fast and intervene in those cases with phototherapy, and in serious cases, blood transfusion. For babies that fall within the range of expected values, we simply watch the infant for a time. Good feeding is important during this period of watchful waiting to help a newborn get rid of the bilirubin through the gut.
Why do some babies develop too much bilirubin?
When a newborn’s bilirubin level starts rising quickly above the expected values we need to figure out why. There are only two possibilities: bilirubin is being produced too quickly (red blood cell breakdown) or it isn’t being excreted properly. Let’s look at each in detail:
Overproduction of Bilirubin
As we said earlier, babies tend to break down red blood cells a bit quicker than adults do. Some conditions aggravate this. Any baby with a traumatic delivery, lots of bruising, or a large collection of blood under the scalp has extra blood to be broken down and can be at risk for higher bilirubin levels. Underlying blood disorders like glucose-6-phosphate dehydrogenase (G6PD) deficiency can lead to critically high jaundice. Other blood disorders that affect the shape of red blood cells, like hereditary spherocytosis, can lead to increased destruction of red blood cells and therefore, increased bilirubin production.
A very common cause of red blood cell destruction in a newborn is blood group incompatibility. Our immune systems learn early on to recognize ‘self’ and not to attack our own tissues. Like all cells, red blood cells have surface markers that the immune system regularly surveys. If they are recognized as ‘self’ everything is fine. If not, the immune system attacks. ABO or Rh blood group incompatibility between mother and baby can cause significant problems. Antibodies produced by a mother’s body can attack a newborn’s blood cells, destroying them and increasing bilirubin and jaundice.
Problems with Excretion of Bilirubin
If bilirubin is not properly being processed or excreted from the liver, this can lead to jaundice. Rarely, babies are born with obstruction of this pathway and this must be determined in a timely fashion and surgically corrected. Far more frequent are difficulties with getting the bilirubin out of the gut and into the stool. Two of the most commonly cited problems here are ‘breastfeeding jaundice’ and ‘breast milk jaundice.’
Breastfeeding jaundice is common in the first week of life and really has very little to do with breast milk per se. This term really means that the newborn isn’t getting very much to eat. Without anything passing through the gut, there is no vehicle for the bilirubin to get out. A baby needs to stool to remove bilirubin and if the baby isn’t eating, he won’t stool. This is called breastfeeding jaundice because it happens most frequently in breastfed babies when mom’s milk hasn’t come in yet. For a few days, the baby gets very little to eat. (There is nothing wrong with this in most instances: newborns go through a very sleepy period during the first 24 hours of life anyway, and few babies feed vigorously right off the bat.) While some may disagree here, if the bilirubin is getting too high I often suggest to breastfeeding mom’s to supplement after each breastfeeding to make sure the baby is getting a bit. Some argue that this is detrimental to breastfeeding but I have seen it go very well many times. Sarah and I did this with our own, who had a significant jaundice, and she was breastfeeding solely and without any ill effects of a few supplemented bottles early on. The way I see it, being forced to re-enter the hospital for phototherapy is not a good thing. If a few supplemental bottles of formula help to prevent this situation, then they are well worth it.
Breast Milk Jaundice
Breast Milk Jaundice begins toward the end of the first week of life and may progress for up to 12 weeks in a breastfed baby. In these cases, the breast milk itself has a factor, yet to be determined, which causes reuptake of bilirubin by the gut. The bilirubin is excreted out of the liver and into the gut and is reabsorbed later back into the baby’s bloodstream before it can be passed out in the stool. In these cases, it is important to make sure the baby is getting enough to eat with accurate weights at the pediatrician’s office and to make sure nothing else is going wrong. If your pediatrician carefully looks for the more serious causes of jaundice and comes up negative, it is likely breast milk jaundice. There is no evidence to suggest any ill effects from this prolonged, low level jaundice. Switching to formula will make the jaundice go away but this is not really necessary. A small amount of formula (about 5 ml) can be given after each feed and this sometimes helps, but breast milk jaundice just goes away on its own after a few weeks without any interventions.
As you have seen throughout the article, the majority of infants with an expected level of jaundice can just be watched carefully. The most important thing for parents to do is make sure the baby is feeding well. Many babies with ABO or Rh incompatibility and others will need intervention. These babies are treated with phototherapy either in the hospital or at home. IV fluids and even blood transfusions are sometimes used. It is important to understand that bilirubin levels over 20 need to be monitored very carefully. Kernicterus is a serious condition. Talk to your pediatrician throughout the process. In most infants that require therapy, the jaundice simply goes away but persistent jaundice after the first week should always be carefully evaluated for a cause.
Matthew Toohey, MD. April 2011.