Neonatal jaundice: what it is and when to get help

Newborn · Health · Reviewed 20 June 2026 · All articles

It is one of the most common surprises of the first days after birth: your baby's skin and the whites of their eyes take on a yellowish tint. For most families this is a brief, harmless episode. But because a small number of babies develop very high bilirubin levels that need prompt treatment, hospitals check every newborn carefully. Understanding what is happening, what the checks involve, and which signs need urgent attention will help you feel less anxious and know when to act.

What jaundice is and why it happens

Jaundice is the yellow discolouration caused by a build-up of bilirubin in the blood. Bilirubin is produced when red blood cells break down. Newborns have a higher number of red blood cells at birth than they will need once they are breathing air, so there is a natural surge in red cell breakdown in the first days. At the same time, a newborn's liver is not yet fully efficient at processing and excreting bilirubin, so levels rise before the liver catches up.

This pattern, called physiological jaundice, is not a disease. It is a predictable part of the newborn transition. In full-term babies it typically appears on day 2 or 3 of life, peaks around day 4 or 5, then gradually fades over the following week. By day 10 to 14 most babies are completely clear. In premature babies the process takes longer because their livers are less mature.

Pathological jaundice is different. It appears within the first 24 hours of life, rises unusually fast, or reaches very high levels. It can be caused by blood group incompatibility between mother and baby (such as Rh or ABO incompatibility), certain inherited red cell conditions, or infection. Pathological jaundice always needs investigation and usually treatment.

How bilirubin is measured

The most common first-line tool is the transcutaneous bilirubinometer, known in Italy as the icterometro transcutaneo. A midwife or nurse holds a small probe gently against the baby's skin, usually on the forehead or sternum, and the device uses light to estimate the bilirubin level in the tissues within seconds. It is painless and does not require a blood test. Italian maternity wards and neonatal units have been using transcutaneous bilirubinometry as a screening tool for over a decade, consistent with guidance from the Istituto Superiore di Sanita (ISS) and from international paediatric bodies.

If the transcutaneous reading is above a threshold, or if there is any clinical concern, the team will take a small blood sample, usually from the baby's heel, to measure the actual serum bilirubin level in micromoles per litre (or milligrams per decilitre in some countries). This serum bilirubin is the definitive measurement used to guide treatment decisions.

Clinicians plot the result on a nomogram, which is a chart that compares the bilirubin level against the baby's exact age in hours. The 2022 American Academy of Pediatrics (AAP) clinical practice guidelines on hyperbilirubinemia use a risk-stratified nomogram that takes into account gestational age, whether the baby is breastfeeding, and other risk factors. The principle is the same in Italian neonatal units: the same number means something different at 24 hours than at 96 hours, because the trajectory matters as much as the absolute figure.

Phototherapy: blue light treatment

When bilirubin levels cross the treatment threshold for that baby's age and risk profile, the standard treatment is phototherapy, called fototerapia in Italian hospitals. The baby is placed under banks of blue-spectrum LED lights (or sometimes on a fibre-optic blanket) wearing only a nappy and protective eye patches. The blue light penetrates the skin and converts bilirubin into water-soluble forms that the body can excrete in urine and stool without needing the liver to process them first.

Phototherapy is very safe. The main considerations in practice are:

• The baby needs to stay under the lights as continuously as possible. Feeds and nappy changes can happen, but time away from the lights should be kept short.
• Regular feeding is important because bilirubin is excreted partly through the gut. Frequent breastfeeds or formula top-ups keep the gut moving and support clearance.
• The baby needs to stay well hydrated. If breastfeeding alone is not providing enough milk in the first days, the team may recommend supplementing while phototherapy is underway.
• Bilirubin is re-checked every 6 to 12 hours to monitor the response. Most babies show a meaningful fall within 24 hours and are clear of phototherapy within 48 hours.

Intensive phototherapy uses higher-intensity lights or multiple light sources for babies with very high levels or fast-rising bilirubin. In rare cases where bilirubin does not respond adequately, an exchange transfusion is performed to rapidly reduce circulating bilirubin. This is now uncommon in high-income countries precisely because screening and timely phototherapy catch most cases before levels become critical.

Breast milk jaundice and breastfeeding jaundice

These are two distinct conditions that are often confused, and it is worth understanding the difference clearly because the management is different.

Breastfeeding jaundice (also called inadequate intake jaundice) occurs in the first week. When a baby is not feeding effectively, they do not pass enough meconium and early stools. Bilirubin is excreted through the gut, so if the gut is not moving well, bilirubin is reabsorbed. This type of jaundice is a signal to check feeding. The solution is almost always to improve breastfeeding technique, feed more frequently (8 to 12 times in 24 hours), and in some cases offer expressed milk or formula as a supplement until supply is established and the baby is feeding well. Stopping breastfeeding is not the answer and is rarely recommended.

Breast milk jaundice is a separate and well-documented condition. It begins after day 5 of life, once mature milk has come in, and can persist for 3 to 6 weeks. The exact mechanism is not fully understood, but certain factors in mature human milk appear to compete with the liver's bilirubin-processing pathway, leading to a slower but prolonged mild elevation of bilirubin. Levels in breast milk jaundice are almost always in a safe range. The baby feeds well, gains weight, produces plenty of wet and dirty nappies, and is alert and settled.

In breast milk jaundice, the current guidance from the AAP and from Italian paediatric societies is clear: do not stop breastfeeding. Breastfeeding should continue throughout. The jaundice will resolve on its own. If the bilirubin level is unusually high, your paediatrician may suggest briefly interrupting breastfeeding for 24 to 48 hours to see if levels drop (which they will in true breast milk jaundice), but this is mainly a diagnostic step. Continuing to breastfeed alongside phototherapy is entirely compatible when treatment is needed.

Warning signs and when to seek help urgently

Most jaundice resolves without drama. The following signs mean you should contact your midwife, paediatrician, or the nearest emergency department without delay:

• Jaundice appears in the first 24 hours of life (always abnormal and needs urgent investigation).
• The yellow colour is spreading rapidly or reaching the lower legs and feet. Jaundice that extends below the knees usually indicates a high bilirubin level.
• The baby is difficult or impossible to wake for feeds.
• The baby has an unusually high-pitched cry or is very floppy.
• Feeding is very poor or the baby is not producing adequate wet nappies.
• Jaundice is still present at 3 weeks of age. Prolonged jaundice beyond 21 days in a formula-fed baby, or beyond 4 weeks in a breastfed baby, should be investigated to rule out liver conditions such as biliary atresia. One important early test is to check whether the baby's stools are pale or chalky, which can indicate a liver or bile duct problem.
• Your instinct says something is not right. Parents often notice subtle changes before any clinical sign becomes obvious. Always call if you are concerned.

If you have been discharged from the maternity unit and are not sure whether your baby's jaundice is worsening, a straightforward first step is to contact your community midwife. In the Italian system, the ostetrica (community midwife) or the paediatrician assigned to the child through the Servizio Sanitario Nazionale (SSN) is the appropriate first point of contact. Most hospitals also operate a neonatal advice line and will never mind you calling to describe your concerns.

Frequently asked questions

Is jaundice in newborns dangerous?

Most newborn jaundice is physiological and resolves on its own within two weeks. However, very high bilirubin levels can, in rare cases, cause brain injury (a condition called kernicterus or acute bilirubin encephalopathy). That is why hospitals screen all newborns and treat promptly when levels are elevated. Contact your midwife or paediatrician if your baby looks very yellow, is difficult to wake, or is feeding poorly.

How long does newborn jaundice last?

In most full-term babies, physiological jaundice appears on day 2 or 3, peaks around day 4 or 5, and clears by 10 to 14 days. In preterm babies and in breast milk jaundice it can persist for up to 3 weeks or occasionally longer, though at lower, safe levels. If jaundice is still visible beyond 3 weeks in a formula-fed baby or beyond 4 weeks in a breastfed baby, ask your paediatrician to investigate further.

Does breastfeeding cause jaundice?

There are two related but distinct situations. Breastfeeding jaundice occurs in the first week when a baby is not feeding often enough and bilirubin rises because less meconium is passed. Breast milk jaundice is a separate condition that starts after day 5 and can last several weeks, caused by substances in mature breast milk that slow bilirubin clearance. In neither case does it mean you should stop breastfeeding without first talking to your doctor or midwife.

What is phototherapy and is it safe?

Phototherapy uses special blue-spectrum lights that convert bilirubin in the skin into a form the body can excrete without liver processing. It is very safe and well established. The baby is undressed (apart from a nappy and eye protection) and placed under the lights. Regular feeds are important to support hydration and gut transit. Most babies need 24 to 48 hours under the lights before bilirubin falls to a safe level.

Trusted sources

• NHS (UK): Newborn jaundice overview
• American Academy of Pediatrics: Clinical Practice Guideline: Management of Hyperbilirubinemia in the Newborn Infant 35 or More Weeks of Gestation (2022)
• Istituto Superiore di Sanita (ISS): Salute perinatale e neonatale

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