What causes physiological jaundice in newborns?

Physiological jaundice in newborns is primarily caused by immature hepatic function. In the first few days after birth, the liver of a newborn is still developing its capability to conjugate and excrete bilirubin. Bilirubin is a byproduct of the breakdown of red blood cells, and when the liver is not yet fully functional, it can result in an accumulation of unconjugated bilirubin in the bloodstream, leading to jaundice.

This condition typically presents in the first week of life and is considered normal as long as bilirubin levels rise and fall within typical ranges, related to the neonate's age in days. The immaturity of the hepatic enzyme systems, such as those responsible for conjugating bilirubin, means that newborns are particularly susceptible to this condition in their early days of life.

While factors like maternal infection, excessive alcohol intake, or inadequate feeding frequency can contribute to jaundice or exacerbate it, they are not the primary causes of physiological jaundice. Rather, physiological jaundice is a natural response to the newborn’s developing liver function.