Newborn Jaundice: What UK Parents Need to Know

Seeing your newborn turn a slight shade of yellow is alarming — but neonatal jaundice is one of the most common conditions in newborns, affecting up to 6 in 10 babies born at term and even more babies born prematurely.

What is newborn jaundice?

Jaundice is a yellowing of the skin and whites of the eyes caused by a build-up of bilirubin — a yellow pigment produced when red blood cells break down.

Newborns have a high turnover of red blood cells and their livers aren't yet mature enough to process bilirubin quickly. This is called physiological jaundice and is entirely normal.

When does it appear?

• Day 2–3: Most commonly appears
• Days 5–7: Typically at its peak
• 2–3 weeks: Usually resolves in full-term babies
• Up to 5 weeks: May persist longer in breastfed babies (breastmilk jaundice — more below)

Warning signs that need urgent attention

Call 999 or go to A&E if your baby:

• Has jaundice in the first 24 hours of life
• Jaundice is spreading to arms, legs, or palms
• Has very yellow, orange, or yellow-green skin
• Is difficult to wake or unusually sleepy
• Has a high-pitched cry
• Has pale/chalky white poo or dark wee

Contact your midwife or GP same day if:

• Jaundice lasts more than 2 weeks (3 weeks if premature)
• You're worried about feeding or weight gain

Breastmilk jaundice

Around 1 in 10 breastfed babies develop prolonged jaundice lasting beyond 2 weeks. This is thought to be caused by a substance in breast milk that slows bilirubin breakdown. It is not harmful in the vast majority of cases, but your midwife or health visitor will check bilirubin levels to confirm.

Do not stop breastfeeding because of mild prolonged jaundice — the benefits of breastfeeding far outweigh the risks.

How is jaundice diagnosed?

Midwives use a transcutaneous bilirubinometer (a painless skin probe) to measure bilirubin levels. If levels are borderline, a blood test (heel prick or vein sample) gives a more accurate reading.

The result is plotted on a treatment threshold chart that factors in the baby's age in hours and any risk factors.

Treatment: Phototherapy

If bilirubin levels are above the treatment threshold, your baby will be placed under special blue-spectrum lights (phototherapy). The light converts bilirubin into a form that can be passed in wee and poo.

• Baby lies in a clear cot wearing only a nappy and eye protection
• Treatment typically lasts 24–48 hours
• You can continue to hold and feed your baby during breaks from the lights

More severe jaundice may require an exchange transfusion (very rare) where blood is gradually replaced to lower bilirubin rapidly.

How to help at home

1. Feed frequently — 8–12 times per 24 hours. Frequent feeding helps flush bilirubin out
2. Keep baby alert during feeds — stroke cheeks, undress to vest
3. Don't use sunlight — you cannot safely treat jaundice at home with sunlight
4. Keep all midwife and GP check-ups — bilirubin levels are monitored until resolved

Will jaundice affect my baby long-term?

In the vast majority of cases, physiological and breastmilk jaundice resolves without any lasting effects. Severe untreated jaundice can cause brain damage (kernicterus) — but this is exceptionally rare in the UK thanks to routine monitoring of all newborns.

Track feeding and nappy output with TinyYears

When managing jaundice, your midwife will ask about feed frequency, wet nappies, and poo colour. Logging this in TinyYears gives you accurate data at a glance — and peace of mind that you're on track.