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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
Types of jaundice: - unconjugated hyperbilirubinaemia: potentially toxic; may be physiological or pathological
- conjugated hyperbilirubinaemia: non toxic; always pathological.
For most babies, jaundice is not an indication of an underlying disease, and
this early jaundice (termed 'physiological jaundice') is generally 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 these babies
- prolonged jaundice is generally harmless, but can be an indication of serious
liver disease
Jaundice has many possible causes, including blood group incompatibility (most
commonly Rhesus or ABO incompatibility), other causes of haemolysis, sepsis,
liver disease, bruising and metabolic disorders. Deficiency of a particular
enzyme, glucose-6-phosphate-dehydrogenase, can cause severe neonatal jaundice
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:
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