<s>[INST] Causes and types [/INST] Bilirubin is a yellow pigment produced during the typical breakdown of red blood cells. In older babies and adults, the liver processes bilirubin, passing it through the intestinal tract. However, a newborn’s still-developing liver may not be mature enough to do this.

There are two types of newborn jaundice: physiological and pathological.

Physiological jaundice is the most common, accounting for 75%Trusted Source of cases. This just means the baby’s metabolism cannot clear out bilirubin as quickly as it is produced. This type typically develops in a few days and clears up on its own in a few weeks when the breakdown of red blood cells slows and liver function improves.

On the other hand, pathological jaundice means that there is another underlying condition that’s causing a problem with filtering out bilirubin. This type may show up in the first 24 hours after birth.

Possible causes include:

blood type incompatibilities such as rhesus factor (Rh) or ABO
breakdown of red blood cells (hemolysis)
conditions that affect how the body processes bilirubin like Gilbert’s syndrome and Crigler-Najjar syndrome
diabetes in the birthing parent
congenital hypothyroidism
intestinal obstruction
pyloric stenosis
breastmilk jaundice, which is a reaction to substances in the milk
breastfeeding jaundice, which can happen if the baby isn’t feeding well
Pathological jaundice can also be caused by certain medications, such as certain antibiotics.
 Source: Health Line. Link: https://www.healthline.com/health/newborn-jaundice#outlook. Field: Hepatology . Disease: Jaundice </s>