Jaundice

When someone starts looking like they are a Simpsons character, we describe them as having jaundice. This yellowing of the skin is due to bilirubin depositing within the skin, which can happen if you have elevated levels of bilirubin in the body. To make things trickier, there are two types of bilirubin that we are concerned with when we see a jaundiced kiddo. There is unconjugated or indirect bilirubin and conjugated or direct bilirubin. 

Bilirubin bound to albumin, a protein in the blood, is called unconjugated or indirect. Bilirubin that is changed by the liver or UV (ultraviolet) light to a form you can get rid of is called conjugated or direct bilirubin.

It is the unconjugated type that we are most concerned with in babies, as this is the type that can cross the blood-brain barrier and cause a condition called kernicterus or bilirubin encephalopathy. Basically, when this type of bilirubin reaches super high levels, it can cause brain damage to anybody, but we are most concerned about this with our little jaundiced babies. This is why we have very well-researched and strict guidelines for who gets tested for this, how often they get tested, and at what levels we start treatment with things like phototherapy (UV light baby tanning beds) or blood transfusions/exchanges.

Most babies have some mild jaundice in the first few days of life as they start to feed and blood turnover in the body increases. Bilirubin is produced by the breakdown of blood cells, so when the turnover happens, the bilirubin goes up. This happens in all our bodies as we get rid of old blood cells. We get rid of this extra bilirubin by having it get processed in the liver, so we can poop and pee it out, which is the reason our pee is yellow and our poop is yellowish brown (cue NBC the more you know music). Babies who are waiting for their parent’s milk to come in aren’t really doing a lot of peeing and pooping to get this stuff out. Hence the bilirubin can build up and start showing us some yellow Bart Simpson skin. Not to worry; most babies keep this level low and develop nowhere near dangerous levels. But we always check a kiddo’s bilirubin in the hospital to make sure that it is not too high or in danger of getting too high with the help of this handy nomogram:

With this handy chart, we can make a really educated prediction that if their bilirubin is at this level now, it will be at this level later if there are no changes in our care. We base these predictions on baby’s and family’s history. Our job is to not let the bilirubin get too high because then it is already a bit too late to prevent neurologic harm. So from this chart, we make a decision on when the next time the kiddo should be seen in clinic to see if the jaundice has gone up or down, if the kiddo should get another bilirubin test in the next day or so, or if we should start phototherapy to get it down to a safe level (even though we are expecting for normal healthy bilirubin to go up and plateau over the first week of baby’s life). 

Now you may be asking, “How does the baby tanning bed or phototherapy work?” Or, “Why does grandma keep saying to put baby near a window if they look yellow?”

Well, it turns out that UV light has this neat trick of basically doing what the liver can do and changing the bilirubin from that indirect form into the other form that can be peed and pooped out. 

But what about this breast milk jaundice I have heard about?

Great question. Breast milk jaundice is another form of jaundice that some babies get a bit later than the previously discussed jaundice; it is usually less of a concern and due to a variety of things in mom’s milk. Scientists are not 100% sure which thing in mom’s milk or which effect of breast milk in the baby’s body causes this, but we do know that it has to do with mom’s milk. Mostly it is attributed to an enzyme in mom’s milk. High levels of beta-glucuronidase in some moms’ breast milk will prevent the liver from doing its full job of changing the bilirubin to its pee- and poo-out form. We will still check on baby’s bilirubin levels during this breast milk jaundice time now and then, but this form of jaundice can last weeks because babies need to eat, right? However, if it hits a month or more of jaundice and parents and their pediatrician want to just get rid of this, then a day or two of giving baby formula will accomplish this. 

Now why would breast milk want to do this? Well if you ask our anthropology friends, their hunch is that back in the day when we were making large broods to help with hunting and gathering, breast milk and babies developed a way for otherwise healthy babies to not look as healthy to family and get more attention during the first few months of life, even with a baker’s dozen of kids running around vying for attention from mom. This could also explain why we often see more breast milk jaundice with each subsequent pregnancy and delivery rather than on the first baby. Is this true? I dunno, but it does make some sense of this weird breast milk trait.