Key point: newborn jaundice is common and usually temporary. It is caused by a build-up of bilirubin. Whether jaundice is harmless cannot be decided from skin colour alone: the baby's age in hours, gestational age, feeding, general condition and measured bilirubin level all matter.
Visible jaundice during the first 24 hours of life needs urgent assessment. Jaundice that becomes more marked, a baby who is difficult to wake or feeds poorly, dark urine or very pale stools also require professional advice.
What is bilirubin?
When red blood cells are broken down, bilirubin is produced. The liver processes it so the body can eliminate it. Newborn babies have high red-cell turnover and an adapting liver, which is why many become mildly yellow during their first days.
How can jaundice be recognised?
The classic sign is yellowing of the skin and whites of the eyes. On darker skin it may be harder to recognise. Visual inspection cannot reliably estimate bilirubin concentration.
Why is jaundice in the first 24 hours different?
Visible jaundice in the first 24 hours is not the usual physiological pattern. NICE recommends urgent serum bilirubin measurement and medical review.
What happens after 24 hours?
After the first day jaundice is much more common, but suspected jaundice still needs appropriate bilirubin measurement. Results are interpreted according to exact postnatal age, gestational age and clinical context.
Why does gestational age matter?
Babies born earlier can be more vulnerable to significant hyperbilirubinaemia. Treatment and monitoring thresholds therefore depend on the individual baby.
Breastfeeding and jaundice
Breastfeeding can usually continue. Feeding support is important because ineffective or infrequent feeding may reduce milk intake and bilirubin elimination. Supplementation decisions should be based on clinical assessment rather than routine.
How do clinicians measure bilirubin?
A transcutaneous bilirubinometer can estimate bilirubin through the skin; serum bilirubin is measured from blood. NICE recommends serum measurement for jaundice in the first 24 hours and in babies born before 35 weeks.
What is phototherapy?
If bilirubin reaches the treatment threshold appropriate to the baby's age and gestation, phototherapy may be recommended. This is controlled medical treatment using light of a specific spectrum.
Why not use sunlight?
NICE advises against sunlight as treatment for hyperbilirubinaemia. Sunlight does not provide a controlled therapeutic dose and can expose a newborn to overheating and skin injury.
Which signs need prompt medical advice?
Seek prompt advice if yellowing increases, feeding becomes poorer, the baby seems unusually sleepy, or there are dark urine or pale stools. Immediate assessment is needed for a baby who is very difficult to wake, will not feed, becomes unusually floppy or stiff, has abnormal movements, breathing difficulty or an abnormal temperature.
How long can jaundice last?
NICE defines prolonged jaundice as lasting more than 14 days in babies born at 37 weeks or later and more than 21 days in babies born before 37 weeks. These situations need further assessment.
Why is kernicterus mentioned?
At very high levels, unconjugated bilirubin can be neurotoxic. Kernicterus is a rare but serious complication. Screening, measurement and treatment are designed to prevent it; ordinary jaundice does not mean a baby is likely to develop kernicterus.
Can severity be judged by colour?
No. Skin pigmentation, lighting and observer experience all affect visual assessment. Do not delay measurement because yellowing seems mild.
Which babies receive closer monitoring?
Factors include birth before 38 weeks, a sibling who previously needed phototherapy, planned exclusive breastfeeding and visible jaundice in the first 24 hours. Other clinical factors may also alter monitoring.
Should a sleepy jaundiced baby be woken for feeds?
A sleepy baby may need waking to maintain adequate feeding. However, if the baby is unusually difficult to wake or cannot feed effectively, seek prompt medical advice.
Key takeaways
- Jaundice is common, but severity cannot be judged by sight alone.
- Jaundice in the first 24 hours needs urgent assessment.
- Bilirubin is interpreted according to exact age in hours and gestational age.
- Breastfeeding can usually continue and feeding support matters.
- Sunlight is not a substitute for medical phototherapy.
- Unusual sleepiness, poor feeding, pale stools, dark urine or worsening jaundice need advice.
Verified sources
- NICE — Jaundice in newborn babies under 28 days
- NHS — Jaundice in babies
- American Academy of Pediatrics — Management of Hyperbilirubinemia
- MSD Manual — Jaundice in the Newborn
- Cambridge University Hospitals NHS
- NHS — Newborn jaundice treatment
General information only. Newborn jaundice must be interpreted in its clinical context. If you are concerned, contact your maternity unit, midwife or doctor.
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