How Do Newborns Get Jaundice? | What Parents See First

A yellow tint in a newborn’s skin can make your stomach drop. Many babies turn a little yellow in the first week and then pink back up as feeding settles and the liver catches up. Still, jaundice can also be a warning sign when it starts early, rises fast, or comes with a baby who won’t wake or won’t feed.

This article explains where jaundice comes from, what the timing can tell you, how it’s measured, and what treatment looks like when levels climb. It’s written so you can spot patterns, ask sharper questions at checkups, and know when to call right away.

How Do Newborns Get Jaundice? Common Causes And Timing

Newborn jaundice is the yellow color you see when bilirubin builds up in the blood. Bilirubin is made as red blood cells break down. The liver changes bilirubin so it can leave the body in stool.

Why the first week is a setup for jaundice

Before birth, the mother’s body clears much of a baby’s bilirubin. After delivery, that work shifts to the baby’s liver. A newborn liver is still maturing, so clearance is slower at first. At the same time, newborns have lots of red blood cells, and those cells turn over quickly. More turnover means more bilirubin to clear.

Why feeding changes bilirubin levels

Bilirubin leaves the body in poop. In the first days, babies pass meconium, then lighter stools. If milk intake is low early on, stools can be less frequent, so bilirubin can stay higher. This is why newborn teams talk so much about feeds and diapers during jaundice checks.

Timing that needs extra attention

When jaundice starts can point to what’s driving it. Yellowing in the first 24 hours is a red flag and needs prompt medical evaluation. Yellowing that lingers beyond two weeks also needs a closer look, since longer-lasting jaundice can be tied to different bilirubin types or bile flow problems.

What Bilirubin Is And Why Skin Turns Yellow

Bilirubin circulates in the bloodstream and can move into skin and the whites of the eyes, causing the yellow tint. Clinicians often separate bilirubin into two forms:

• Unconjugated bilirubin (indirect): not yet processed by the liver; this is the usual pattern in early newborn jaundice.
• Conjugated bilirubin (direct): processed by the liver and ready to leave the body through bile and stool; this pattern needs a workup when elevated.

Most early jaundice is unconjugated and peaks in the first week as the liver and feeding routine catch up. Direct (conjugated) jaundice is less common and can signal a liver or bile duct problem.

Common Types Of Newborn Jaundice

You may hear these terms during a newborn stay or follow-up visit. They describe the same core idea—bilirubin is rising—yet the “why” can change the plan.

Physiologic jaundice

This is the common newborn transition pattern. It usually starts after the first day of life and fades as the baby feeds more and clears bilirubin faster.

Jaundice linked to low early intake

Some babies take a few days to coordinate latch, suck, and swallow, or they’re sleepy and hard to rouse. If intake is low, stool output can be low, which slows bilirubin exit. Fixing intake often brings bilirubin down.

Breast milk jaundice

Some breastfed babies stay a bit yellow longer, often after the first week, while still feeding and gaining well. Clinicians may label this breast milk jaundice after other causes are ruled out.

Jaundice from faster red blood cell breakdown

When red blood cells break down faster than usual (hemolysis), bilirubin can rise quickly. Triggers include blood group incompatibility (ABO or Rh), inherited red cell conditions, and enzyme problems such as G6PD deficiency. Early onset and a steep rise raise concern for this pattern.

Risk Factors That Raise The Odds Of Higher Bilirubin

Risk factors don’t guarantee a baby will need treatment. They help clinicians decide who needs earlier testing and tighter follow-up.

• Earlier gestational age (late preterm)
• Bruising or a cephalohematoma (blood under the scalp)
• Blood type mismatch between parent and baby
• Sibling history of phototherapy
• G6PD deficiency risk based on family history or ancestry patterns
• Low early intake with fewer wet diapers or stools

How Clinicians Measure Jaundice

Skin color helps start the conversation, yet lighting and skin tone can fool the eye. Measurement makes the plan safer.

Transcutaneous bilirubin screening

A handheld meter estimates bilirubin through the skin. It’s quick and painless. If the reading is high or the baby has higher risk, clinicians confirm with a blood test.

Total serum bilirubin blood test

A blood test measures bilirubin directly. The number is interpreted by the baby’s age in hours, gestational age, and certain medical risks. A level that is fine at one age can cross a treatment line a day later, since bilirubin can keep rising after discharge.

Many hospitals and clinics use the American Academy of Pediatrics (AAP) guidance to plan screening, follow-up timing, and treatment thresholds. AAP hyperbilirubinemia guidance links to the clinical resources used in routine newborn care.

When Jaundice Needs A Same-Day Call

Most jaundice is mild. Still, high bilirubin can injure the brain if not treated. The earliest warning signs often show up in feeding and behavior.

• Yellowing that starts in the first 24 hours
• Hard to wake for feeds, or feeds that suddenly get worse
• High-pitched cry or unusual irritability
• Limpness or stiff arching
• Fewer wet diapers than expected for age
• Pale or chalky stools, or dark urine staining the diaper

The CDC notes that severe hyperbilirubinemia can lead to kernicterus, which is why early identification and management are part of standard newborn care. CDC notice on jaundice guidance summarizes this risk.

Feeding And Diapers: The Fastest Day-To-Day Levers

When jaundice is tied to low intake, a small change in feeding can show up quickly in diaper output and bilirubin trends. Newborn teams often aim for frequent feeds in the first days, with a plan for sleepy babies who don’t wake on their own.

What to watch at home

• Wet diapers rising day by day
• Stools shifting from dark meconium toward green, then yellow
• Feeds that feel more active, with swallowing you can hear or see

If intake is not meeting goals, clinicians may suggest short-term supplementation while working on milk transfer. The plan should include clear follow-up and a clear point for reassessment.

Bilirubin Timing And Typical Next Steps

Clinicians don’t treat based on “yellow” alone. They combine the bilirubin value with age in hours and risk profile. Treatment is set to start before bilirubin reaches ranges linked with neurologic injury.

Here’s a practical view of common patterns and what often happens next.

Pattern You Notice	What It Can Mean	What Often Happens Next
Yellowing in first 24 hours	Possible hemolysis or early illness	Same-day bilirubin blood test; testing for hemolysis; tight follow-up
Day 2 to day 5 yellowing	Common transition pattern	Screening level; feeding plan; follow-up timed by hour-based thresholds
Baby sleepier and feeding less	Bilirubin rising, intake falling	Urgent level check; intake plan; treat if thresholds are met
Bruising or scalp bump from birth	Extra blood breaking down	Earlier checks; watch for faster rise
Rapid rise after discharge	Peak happening at home	Urgent recheck; treatment decisions based on age in hours
Yellowing beyond two weeks	Needs bilirubin type split	Direct vs indirect bilirubin; check for bile flow issues
Pale stools or dark urine	Possible cholestasis	Same-day medical evaluation and lab work

Phototherapy: What It Does And What It Looks Like

Phototherapy uses blue light to change bilirubin into forms that a baby can pass more easily. Babies wear eye shields and stay under the lights, with breaks for feeds and care based on the unit’s setup.

The NHS notes that treatment is usually needed only when bilirubin is high, and phototherapy is the main way to lower it. NHS newborn jaundice treatment explains how it works and what parents can expect.

Questions worth asking while your baby is under lights

• How often will bilirubin be rechecked?
• What number or trend would allow stopping phototherapy?
• What’s the feeding plan while my baby is sleepy?

When More Intensive Care Is Used

If bilirubin rises quickly or reaches a high-risk range, clinicians may use intensive phototherapy and test for the trigger, such as hemolysis. Treatment may also include IV medicines in select hemolytic cases.

Exchange transfusion

Exchange transfusion is reserved for cases where bilirubin is dangerously high or rising despite intensive phototherapy. It replaces part of the baby’s blood with donor blood to lower bilirubin and remove antibodies that drive hemolysis. MedlinePlus exchange transfusion describes the procedure and why it is used.

Care Step	When It’s Used	What Parents See
Feeding plan adjustment	Mild to moderate jaundice with low intake	More frequent feeds, latch help, diaper and weight tracking
Repeat bilirubin checks	Borderline levels or rising trend	Clinic or lab visits timed by age in hours
Phototherapy	Level meets treatment threshold	Blue lights, eye shields, rechecks every set interval
Intensive phototherapy	Fast rise or level near escalation range	More light surface area, tighter monitoring
IVIG (select hemolysis cases)	Antibody-driven bilirubin rise	IV medicine with monitoring during infusion
Exchange transfusion	Danger range or failure of intensive lights	NICU procedure with close monitoring

After Discharge: A Quick Home Checklist

Use this list for the next couple of days, when sleep is scarce and it’s easy to second-guess everything.

• I know the last bilirubin result and when the next check is scheduled
• My baby is feeding often, or I have a plan for sleepy feeds
• Wet diapers are rising day by day
• Stools are moving off meconium and getting lighter
• I know the same-day call signs: first-day jaundice, worsening sleepiness, poor feeds, pale stools, dark urine
• I have the after-hours phone number for the newborn unit or clinic