Even in healthy full-term newborns, there is an increased bilirubin load owing to increased red blood cells (RBC) mass and a decreased RBC lifespan. Healthy adults have a normal TSB level of less than 1mg/dl in contrast to neonates, where TSB levels are physiologically higher. Physiological jaundice accounts for 75% of neonatal hyperbilirubinemia and results from a physiological alteration in neonatal bilirubin metabolism. Unconjugated hyperbilirubinemia is the more common type and is either physiological or pathological. Unconjugated Hyperbilirubinemia(UHB) or Indirect Hyperbilirubinemia There are two distinct types of Neonatal hyperbilirubinemia. Despite advances in care and management of hyperbilirubinemia, it remains a significant cause of morbidity and mortality. Treatment of CHB is more complex and depends mainly on the etiology. Phototherapy and exchange transfusions are the mainstay of treatment of UHB, and a subset of patients also respond to intravenous immunoglobulin (IVIG). Severe hyperbilirubinemia can cause bilirubin-induced neurological dysfunction (BIND) and, if not treated adequately, may lead to acute and chronic bilirubin encephalopathy. Preterm infants and those born with congenital enzyme deficiencies are particularly prone to the harmful effects of unconjugated bilirubin on the central nervous system. The etiology of pathological UHB and CHB is vast and varied. Unconjugated hyperbilirubinemia (UHB) is the cause of clinical jaundice in most neonates, but some infants with jaundice have conjugated hyperbilirubinemia (CHB), which is always pathological and signifies an underlying medical or surgical cause.

In most cases, it is a mild, transient, and self-limiting condition and resolves without treatment referred to as 'physiological jaundice.' However, it is imperative to distinguish this from a more severe form called 'pathological jaundice.' Failure to identify and treat this entity may result in bilirubin encephalopathy and associated neurological sequelae.

Approximately 60% of term and 80% of preterm newborns develop clinical jaundice in the first week after birth. It is the most commonly encountered medical problem in the first two weeks of life and a common cause of readmission to the hospital after birth. The term jaundice derives from the French word 'jaune,' which means yellow. Neonatal jaundice or neonatal hyperbilirubinemia results from elevated total serum bilirubin (TSB) and clinically manifests as yellowish discoloration of the skin, sclera, and mucous membrane.

Pathological jaundice newborn