What is bilirubin in a newborn?
by Dr. Pamela Bandelaria, pediatrician
Have you ever wondered why your baby can sometimes look yellow? This is what doctors call jaundice. It occurs commonly in newborns and may be due to many causes. The yellow color usually appears after the second day of life and persists for two weeks. The color change is due to bilirubin, which is a fat-soluble pigment that accumulates in the skin. Bilirubin is a byproduct of the breakdown of heme, the iron which mostly comes from old red blood cells. In the womb, this fat-soluble (also called indirect or unconjugated) form of bilirubin is usually passed through the placenta without any difficulty. However, as the baby is born, the fat-soluble bilirubin is brought to the baby’s liver to be converted first into a water-soluble form before excretion in bile. In normal newborn babies, there may be increased bilirubin production due to a large volume of fetal red blood being cells broken down. The baby’s immature liver can be overwhelmed as it is still adjusting to its new role as a detoxifier. Both of these things may lead to the buildup of bilirubin in the body and accumulation in the skin. A normal bilirubin level is 1-3mg/dL and increases at a rate of <5mg/dL/day.
The yellowish color of the skin may be normal and not be a cause of concern. Jaundice of this type is called physiologic jaundice and usually follows a certain pattern. Physiologic jaundice begins during the second to fourth day after birth and is visible when babies have bilirubin levels of 5-6mg/dL. It usually starts in the face and proceeds in a downward fashion as serum bilirubin levels increase. A yellowish color up to the abdomen is estimated to be a bilirubin level of 15mg/dL. These decrease to 2mg/dL by the 5th to 7th day of life. Breastfeeding may also be attributed to an incidence of jaundice in the newborn, aptly termed breastfeeding jaundice. In most cases, as long as the baby appears well and the yellowish color lessens or disappears by the first week of life, there is no cause for concern.
There are certain instances when a yellow color warrants a doctor’s evaluation. A yellowish color of the skin within the first 24 hours is a cause of concern and must be evaluated. Similarly, a yellowish color persisting for more than two weeks of life must also be evaluated. These do not follow the pattern of physiologic jaundice and the yellowish color of the skin may be due to an underlying disease. If the yellowish color also reaches the soles of the baby’s feet, it may indicate a high bilirubin level (around 20mg/dL or higher). Extremely high bilirubin levels can cause seizures and brain dysfunction, an effect called kernicterus.
Increased bilirubin may or may not be normal in a newborn. What is important is that you know what to look out for and when to bring your baby to the physician. Now you can focus on your baby’s growth and milestones!
References:
Kliegman, R. St Geme, J. Blum, N. Shah, S. Tasker, R. Wilson, K. Behrman, R. (2019). Nelson textbook of pediatrics (Edition 21.). Philadelphia, PA: Elsevier.
Mitra S, Rennie J. Neonatal jaundice: aetiology, diagnosis and treatment. Br J Hosp Med (Lond). 2017 Dec 2;78(12):699-704. doi: 10.12968/hmed.2017.78.12.699. PMID: 29240507.
National Center for Biotechnology Information (2020). PubChem Compound Summary for CID 5280352, Bilirubin. Retrieved December 21, 2020 from https://pubchem.ncbi.nlm.nih.gov/compound/Bilirubin.
Reiser DJ. Neonatal jaundice: physiologic variation or pathologic process. Crit Care Nurs Clin North Am. 2004 Jun;16(2):257-69. doi: 10.1016/j.ccell.2004.02.010. PMID: 15145371.
Woodgate P, Jardine LA. Neonatal jaundice. BMJ Clin Evid. 2011 Sep 15;2011:0319. PMID: 21920055; PMCID: PMC3217664.
