Newborn Jaundice Explained

Jaundice — a yellowing of the skin and whites of the eyes — affects around 6 in 10 babies in the first week, making it one of the most common newborn conditions. Most cases are mild and resolve without treatment, but it's worth understanding both the usual pattern and the exceptions.

Why it happens

Jaundice is caused by a build-up of bilirubin, a substance produced when red blood cells break down. Adults clear bilirubin efficiently through the liver; a newborn's liver isn't yet fully mature, so bilirubin can build up faster than it's cleared, particularly in the first few days.

The usual, harmless pattern

Typically appears on day 2 or 3, peaks around day 5, and fades by 2 weeks (breastfed babies can sometimes have mild jaundice for a bit longer, up to a few weeks, which is usually still not a concern). It's often first visible on the face, then spreads down the body as levels rise, which is why midwives check by pressing gently on the skin to see the underlying colour.

Monitoring and treatment

Midwives check for jaundice as part of routine newborn checks. If levels are high enough to need treatment, phototherapy (special blue light that helps break down bilirubin) is the standard approach, usually done in hospital over a day or two, and very effective. Severe, untreated jaundice is rare in the UK precisely because of this routine monitoring.

When jaundice needs urgent attention

Contact your midwife, health visitor or GP urgently, or go to A&E, if:

• Jaundice appears in the first 24 hours of life (this is different from the usual day 2-3 pattern and always needs same-day assessment)
• Your baby is difficult to wake, feeding poorly, or unusually floppy
• The yellowing seems to be getting worse rather than better
• Jaundice hasn't resolved by 2 weeks (3 weeks if premature)
• Your baby's poo is pale/chalky or urine is dark — this combination can indicate a liver problem needing separate investigation

The takeaway

Mild jaundice in the typical day 2-5 window is common and expected, and routine midwife checks are specifically designed to catch the rare cases that need treatment. Knowing the handful of red-flag signs in advance means you don't need to worry about ordinary jaundice, while still knowing exactly what would prompt a call.