neonatal jaundice

Last reviewed 01/2018

Jaundice is clinically detectable in the newborn when the serum bilirubin levels are greater than 85 micromoles per litre. This occurs in approximately 60% of term infants and 80% of preterm infants in the first week of life. About 10% of breastfed babies are still jaundiced at 1 month

For most babies, jaundice is not an indication of an underlying disease, and this early jaundice (termed 'physiological jaundice') is usually harmless.

Breastfed babies are more likely than bottle-fed babies to develop physiological jaundice within the first week of life

• prolonged jaundice - that is, jaundice persisting beyond the first 14 days -is also seen more commonly in breastfed babies
• prolonged jaundice is usually harmless, but can sometimes be an indication of serious liver disease

Types of jaundice:

• unconjugated hyperbilirubinaemia: potentially toxic; may be physiological or pathological
• conjugated hyperbilirubinaemia: non toxic; always pathological.

Jaundice has many possible causes, including

• blood group incompatibility (most commonly rhesus or ABO incompatibility), other causes of haemolysis (breaking down of red blood cells),
• sepsis (infection),
• liver disease,
• bruising
• and metabolic disorders
  • deficiency of a particular enzyme, glucose-6-phosphate-dehydrogenase, can cause severe neonatal jaundice
  • glucose-6-phosphate-dehydrogenase deficiency is more common in certain ethnic groups and runs in families.

Bilirubin is mainly produced from the breakdown of red blood cells

• red cell breakdown produces unconjugated (or 'indirect') bilirubin, which circulates mostly bound to albumin although some is 'free' and hence able to enter the brain
• unconjugated bilirubin is metabolised in the liver to produce conjugated (or 'direct') bilirubin which then passes into the gut and is largely excreted in stool

Clinical recognition and assessment of jaundice can be difficult, particularly in babies with darker skin tones

Notes:

• bilirubin travels in the blood in two ways; some is bound to albumin and is called conjugated or direct bilirubin whereas the remainder is free, not bound, and is called unconjugated or indirect bilirubin. The terms direct and indirect refer to the way the laboratory tests measure the different forms. Some tests measure total bilirubin and do not distinguish between the two forms
• in young babies, unconjugated bilirubin can penetrate the blood-brain barrier
  • unconjugated bilirubin is potentially toxic to neural tissue
    • entry of unconjugated bilirubin into the brain can cause both short-term and long-term neurological dysfunction (bilirubin encephalopathy)
    • term kernicterus is used to denote the clinical features of acute or chronic bilirubin encephalopathy, as well as the yellow staining in the brain associated with the former
      • risk of kernicterus is increased in babies with extremely high bilirubin levels. Kernicterus is also known to occur at lower levels of bilirubin in term babies who have risk factors, and in preterm babies
        
        
• clinicians should identify babies as being more likely to develop significant hyperbilirubinaemia if they have any of the following factors:
  • gestational age under 38 weeks
  • a previous sibling with neonatal jaundice requiring phototherapy
  • mother's intention to breastfeed exclusively
  • visible jaundice in the first 24 hours of life

Reference:

• NICE (May 2016). Jaundice in newborn babies under 28 days - update.