Jaundice—a yellow tint to a baby's skin and the whites of the eyes—is extremely common in newborns. It affects about 6 out of 10 full-term babies and even more babies born early.

Most newborn jaundice is mild and improves on its own. But bilirubin can occasionally rise high enough to require treatment, so it is important for parents to understand what causes jaundice, what to watch for, and when a baby should be checked.

What causes jaundice?

Jaundice happens when a yellow substance called bilirubin builds up in the blood.

Bilirubin is made naturally as the body breaks down old red blood cells. A newborn produces bilirubin quickly, and the baby's still-developing liver may not clear it as efficiently as an older child's or adult's liver.

This common newborn pattern is often called physiologic jaundice. It usually becomes noticeable after the first 24 hours of life and often becomes more visible over the next several days before improving.

Jaundice that appears during the first 24 hours after birth deserves prompt medical evaluation because it is more likely to have an underlying cause.

Which babies are more likely to have higher bilirubin levels?

Some babies have a greater chance of developing significant jaundice. Risk factors include:

Being born early, particularly before 38 weeks
Having a parent, brother, or sister who required treatment for newborn jaundice
Significant bruising or a scalp hematoma after delivery
Blood-type incompatibility between the baby and mother that causes increased red blood cell breakdown
G6PD deficiency or another inherited red blood cell condition
Feeding difficulties or inadequate milk intake
A bilirubin level that is already relatively close to the treatment threshold before leaving the hospital

Having one of these risk factors does not mean a baby will require treatment. It may simply mean that closer follow-up is important.

Feeding and jaundice

Feeding plays an important role in how the body clears bilirubin.

When a newborn is not taking in enough milk, there is less stool moving through the intestines. This allows more bilirubin to be reabsorbed into the body and can contribute to what physicians call suboptimal intake hyperbilirubinemia.

For breastfed newborns, feeding at least 8 times in 24 hours is generally encouraged during the early days of life.

Parents and clinicians should also pay attention to:

Whether the baby is actively swallowing during feeds
Wet and dirty diapers
Weight loss after birth
Whether the mother's milk supply is increasing as expected

Breastfeeding itself does not cause dangerous jaundice, and most babies with jaundice can continue breastfeeding.

If feeding is difficult, early help from the baby's pediatrician and a lactation consultant can make a significant difference.

What should parents watch for?

Jaundice often becomes noticeable first on the face and may become visible farther down the body as bilirubin rises.

In babies with darker skin, yellowing may be easier to notice in the whites of the eyes, gums, or other less-pigmented areas.

Contact your baby's clinician promptly if:

Jaundice appears during the first 24 hours of life
Your baby seems increasingly yellow
Your baby is feeding poorly
Your baby is unusually sleepy or difficult to wake for feeds
Wet or dirty diapers are decreasing
Your baby has very pale, gray, white, or chalk-colored stools
Your baby's urine appears unusually dark
You are concerned that the jaundice is worsening rather than improving

When does jaundice need urgent medical attention?

Seek urgent medical evaluation if a jaundiced newborn becomes very difficult to wake, feeds very poorly, develops an unusual high-pitched cry, becomes stiff or unusually floppy, repeatedly arches the neck or back, or has abnormal movements.

These symptoms are uncommon but can be signs that bilirubin is affecting the nervous system.

For a possible life-threatening emergency, call 911 or go to the nearest emergency department.

Why does bilirubin matter?

At very high levels, bilirubin can cross into brain tissue.

Severe bilirubin toxicity is rare, but it can cause a permanent form of brain injury called kernicterus, which may lead to hearing loss, abnormal movements, and other neurologic problems.

Fortunately, severe bilirubin injury is uncommon and is largely preventable when jaundice is recognized, measured, followed appropriately, and treated when necessary.

That is why pediatricians pay close attention to jaundice even though the overwhelming majority of jaundiced newborns do very well.

How is jaundice checked?

All newborns should have a bilirubin level checked before leaving the birth hospital.

This is generally done between 24 and 48 hours after birth, or earlier if the baby is discharged before then.

Bilirubin can initially be measured in two ways:

Transcutaneous bilirubin (TcB)

A small light meter is placed against the baby's skin. It is quick and painless.

Total serum bilirubin (TSB)

A small blood sample directly measures bilirubin. This is the definitive measurement used when treatment decisions are needed.

The bilirubin number by itself is not enough to determine whether treatment is necessary.

Your baby's clinician considers:

The bilirubin level
The baby's age in hours
Gestational age at birth
Whether certain medical risk factors are present
How close the bilirubin is to the level at which phototherapy would be recommended

When should my baby be checked again?

There is no single follow-up schedule that is right for every newborn.

Current recommendations base follow-up partly on how close your baby's bilirubin level is to the phototherapy treatment threshold at the time of discharge.

A baby whose bilirubin is well below the treatment level may need routine follow-up, while a baby whose level is closer to the threshold may need to be seen and rechecked much sooner.

Feeding, weight loss, gestational age, and the baby's overall health also influence the timing.

Before leaving the hospital, parents should know:

Their baby's most recent bilirubin result
When the next pediatric visit should occur
Whether another bilirubin measurement is recommended

Keeping that follow-up appointment is important even if your baby looks well.

How is newborn jaundice treated?

Most babies with jaundice do not need treatment. Bilirubin levels fall naturally as feeding improves and the baby's liver becomes better able to process bilirubin.

When treatment is necessary, the most common treatment is:

Phototherapy

Phototherapy uses special blue light to change bilirubin into forms that the baby's body can eliminate more easily.

It is safe, painless, and highly effective.

Babies continue feeding during treatment. When overhead phototherapy lights are used, the baby's eyes are protected.

Additional, more complex treatments may be needed in uncommon situations, but those treatments are beyond the scope of this parent guide and require hospital-based specialist care.

What about sunlight?

Do not use sunlight as a substitute for medical treatment.

Sunlight exposure is difficult to dose safely and reliably and may expose a newborn to overheating or sunburn.

If bilirubin is high enough to require treatment, medically supervised phototherapy is the appropriate treatment.

What if the jaundice does not go away?

Some breastfed babies remain mildly jaundiced for several weeks and are otherwise completely healthy. This is often called breast milk jaundice.

Persistent jaundice still deserves appropriate evaluation.

Parents should contact their baby's clinician if:

A formula-fed baby remains jaundiced at about 2 weeks of age
A breastfed baby remains jaundiced at about 3 to 4 weeks of age
The baby's stools are pale, gray, white, or chalk-colored
Urine is unusually dark
Feeding or weight gain is poor

In these situations, the pediatrician may check both total and direct bilirubin levels to make sure the jaundice is not related to liver or bile-flow problems.

The bottom line

Newborn jaundice is extremely common, and most babies improve without treatment.

The important things are to:

Feed your baby regularly
Pay attention to feeding, diapers, and alertness
Keep newborn follow-up appointments
Have bilirubin measured when your baby's clinician recommends it
Seek care if jaundice appears very early, worsens, or is accompanied by concerning symptoms

Skin color alone cannot tell you whether a bilirubin level is safe.