Jaundice — the yellowish discolouration of the skin and whites of the eyes caused by elevated bilirubin levels in the blood — is one of the most common conditions of the newborn period, and it is also one that generates significant anxiety among parents. Most newborn jaundice is physiological, benign, and self-resolving. A minority of cases require treatment, and a smaller minority are signs of an underlying condition.
Understanding the difference between physiological jaundice (expected and usually not concerning) and pathological jaundice (requiring investigation and treatment) helps parents respond appropriately and seek help promptly when it is needed.
Healthbooq supports parents in tracking newborn health observations including jaundice progression, providing a record that is useful at midwife and health visitor visits.
Why Newborn Jaundice Happens
Bilirubin is a yellow breakdown product of haemoglobin — the oxygen-carrying protein in red blood cells. Newborns have a higher concentration of red blood cells than adults, which are broken down rapidly in the early postnatal period as the circulation adapts to life outside the womb. The bilirubin produced by this breakdown accumulates in the blood while the liver — which processes and excretes bilirubin — completes its maturation.
In term babies, physiological jaundice appears from the second or third day of life (never the first day), peaks around days three to five, and resolves by day ten to fourteen. In preterm babies, jaundice tends to be more pronounced and more prolonged because liver maturation is less complete.
Bilirubin is deposited in the skin and mucous membranes, producing the yellow discolouration. Assessment of jaundice severity requires measurement of serum bilirubin levels, as visual assessment alone is not reliable enough to guide treatment decisions.
When Treatment Is Needed
The threshold for treatment with phototherapy varies by the baby's gestational age and postnatal age and is given as a curve on which the baby's bilirubin level is plotted. Treatment is initiated when the level reaches or exceeds the threshold for the baby's specific age.
Phototherapy — treatment using specific wavelengths of blue-green light — converts bilirubin in the skin to a water-soluble form that can be excreted in urine and stool without liver processing. It is effective, safe, and the standard treatment for jaundice requiring intervention. Babies undergoing phototherapy are placed under phototherapy lamps (or on a phototherapy blanket) with eyes protected. Continuing to feed frequently during phototherapy is encouraged, as feeds help clear bilirubin via stools.
In severe jaundice that does not respond to phototherapy, exchange transfusion may be required. This is now rare.
Jaundice Requiring Prompt Assessment
Jaundice in the first 24 hours of life is never physiological — it requires immediate assessment to identify the cause (typically haemolytic disease — incompatibility between maternal and baby blood groups). Jaundice associated with a sick baby (unwell appearance, poor feeding, fever) requires prompt assessment. Jaundice that persists beyond two weeks in a term baby, or beyond three weeks in a preterm baby, should be assessed to exclude cholestatic conditions (biliary atresia) — the urine and stool colour are important here: pale, chalky stools and dark urine alongside jaundice suggest biliary atresia, which requires urgent surgical referral.
Key Takeaways
Neonatal jaundice — the yellow skin discolouration caused by elevated bilirubin — affects approximately 60% of term newborns and 80% of preterm newborns in the first week of life, and in most cases is physiological (normal), self-limiting, and requires no treatment beyond monitoring. Treatment with phototherapy is needed when bilirubin levels reach thresholds that vary by gestational age and postnatal age. Jaundice that appears within the first 24 hours of life, jaundice in a sick baby, and jaundice persisting beyond two weeks all require medical assessment to exclude pathological causes.
