How Bilirubin is Produced and Removed in Newborn Babies and Why Fed is Best

Bilirubin Metabolism

This is a review for parents on the physiology of jaundice (hyperbilirubinemia) so that they may understand the reason why higher volumes of milk intake reduce the severity of jaundice in newborn babies.  

Before a baby is born, the baby relies on a type of blood called fetal blood that is specifically tailored to life in the womb.  This fetal blood allows babies to remove oxygen from maternal blood as efficiently as possible.  When a baby is born, he must transition to mature blood.  This occurs by the break down of fetal blood cells and increased production of mature blood cells (see the top of the diagram).

The breakdown of fetal blood results in the accumulation of bilirubin in the newborn.  The primary way that bilirubin is removed from the body is through the liver into the intestines (see the bottom of the diagram).  This bilirubin is carried away by milk that passes through the intestines.  Without this milk, the bilirubin is reabsorbed into the blood stream, which leads to increasing levels of bilirubin in the newborn.

When bilirubin levels are high, about a small percentage of bilirubin can be removed through the urine.  This process is aided by the use of phototherapy (or bilirubin lights).  The phototherapy allows bilirubin to dissolve in the urine allowing it to be removed more efficiently.   In addition, phototherapy converts bilirubin, a known brain toxin, to a form that reduces its entry into the brain while enhancing excretion through urine.

However, even in the face of very high bilirubin levels, the majority of bilirubin is still removed through milk passing through the intestines.  For a mother who does not have enough breast milk to give, particularly in the first days of life, supplementation with donor milk or formula are the most effective ways to remove bilirubin and reduce the toxic effects of bilirubin to the brain.  This is the reason why supplemented newborns have lower bilirubin levels than exclusively breastfed newborns.  Getting more milk reduces bilirubin, regardless of the type of milk fed to a baby.

If a baby has hyperbilirubinemia severe enough to require phototherapy, it has been shown that markers of brain injury are already present in the blood.  Brain injury is irreversible, even with phototherapy and supplementation.  The purpose of phototherapy and supplementation at the point when the bilirubin is high enough to require treatment is to prevent any further brain injury from occurring.

Therefore, the safest way to prevent brain injury in jaundiced newborns is to prevent the excessive jaundice from happening by evaluating the amount of milk a mother has, evaluating the newborn for hyperbilirubinemia and dehydration, and finally, listening to a baby's inconsolable cries.  The baby is the only one who knows when they are in distress and in need for more milk.  Supplementation can save the brain and life of an underfed newborn.

References:

Gartner, L. M. Breastfeeding and jaundice. J Perinatol 21 Suppl 1, S25–29; discussion S35–39 (2001).

Watchko, J. F. & Tiribelli, C. Bilirubin-induced neurologic damage--mechanisms and management approaches. N. Engl. J. Med. 369, 2021–2030 (2013).

Sarici, D. et al. Investigation on malondialdehyde, S100B, and advanced oxidation protein product levels in significant hyperbilirubinemia and the effect of intensive phototherapy on these parameters. Pediatr Neonatol 56, 95–100 (2015).