Jaundice in newborns

A majority of newborns become visibly yellow in the first week, which is a physiological process in most cases and a warning sign in a minority.

Why it happens

Babies are born with a high red cell count, and those cells break down after birth, releasing bilirubin.

The newborn liver is immature and processes bilirubin slowly.

Bilirubin is also reabsorbed from the gut, which is why feeding and passing stool matter.

The combination produces a rise in bilirubin that typically peaks around day three to five and then falls.

The timing that matters

The single most useful piece of information.

Jaundice in the first twenty-four hours is always abnormal and requires urgent assessment, because it suggests haemolysis — accelerated breakdown of red cells, most often from blood group incompatibility — or infection.

Jaundice appearing on day two to four, peaking and settling, is the common physiological pattern.

Jaundice persisting beyond fourteen days in a term baby, or twenty-one days in a preterm baby, is prolonged jaundice and needs investigation.

Most prolonged jaundice is benign, frequently associated with breastfeeding, and a proportion is not — biliary atresia is a rare condition where outcomes depend heavily on early surgery, which is why the check is done.

The key sign in that context is pale, chalky stools and dark urine, which should prompt same-day assessment.

How it is assessed

Visual assessment alone is unreliable, particularly in babies with darker skin, which is a recognised source of missed diagnosis.

Transcutaneous bilirubinometers — handheld devices held against the skin — are used for screening.

Blood levels are measured where the reading is high, where the baby is under a certain age, or where there are risk factors.

Results are plotted against age in hours on a treatment threshold chart, which is why the exact age matters and why a number alone means little.

Looking at the whites of the eyes, the gums and blanched skin is more reliable than looking at skin colour alone in a well-lit room.

Treatment

Phototherapy is the standard treatment: light of a specific wavelength converts bilirubin into a form that can be excreted without liver processing.

It is not ultraviolet light and it is not a sunlamp.

The baby is undressed with eyes protected, and feeding continues — frequent feeding is part of treatment because it promotes excretion.

Intensive phototherapy is used for higher levels.

Exchange transfusion is reserved for very high levels or rapid rises and is now uncommon.

Intravenous immunoglobulin is used in some cases of haemolytic disease.

Placing a baby in sunlight is not a recommended treatment and carries risks of burning and overheating.

Why untreated severe jaundice matters

Stated because it explains the caution.

Very high bilirubin can cross into the brain and cause kernicterus, a form of permanent brain injury causing movement disorders, hearing loss and developmental problems.

It is rare in settings with systematic screening and treatment, and essentially all cases are preventable.

Which is the entire reason for the thresholds, the charts and the repeated checks.

Risk factors

Babies more likely to need treatment.

Prematurity, with lower thresholds applying.

Blood group incompatibility between mother and baby.

Bruising or cephalohaematoma from delivery.

A sibling who needed phototherapy.

East Asian ancestry, and G6PD deficiency, which is more common in some populations and which can cause rapid severe jaundice.

Poor feeding and significant weight loss.

And infection.

Feeding and jaundice

An area where advice has sometimes been unhelpful.

Jaundice associated with insufficient intake in the first days — sometimes called breastfeeding jaundice — is addressed by improving feeding, not by stopping breastfeeding.

Breast milk jaundice, which is prolonged and benign, does not require stopping breastfeeding either.

Supplementation may be advised in specific circumstances and should be a clinical decision rather than a default.

Frequent effective feeding is the practical measure that helps most.

What parents should watch for

At home in the first fortnight.

Yellowing appearing in the first day, or spreading down the body to the abdomen, legs, palms and soles.

A baby becoming sleepy, difficult to wake or feeding poorly.

A high-pitched cry or arching.

Pale stools or dark urine at any point.

Jaundice still present at two weeks.

And any deepening rather than fading of the colour.

Any of these warrants contacting a midwife, health visitor or medical service the same day.

General information only, not medical advice. Seek same-day assessment for jaundice in the first 24 hours, jaundice persisting beyond two weeks, or pale stools.