Newborn Jaundice: What It Is, What Causes It, and When to Worry
The yellowish tint that appears on many newborns' skin in the first days of life — jaundice — is one of the most common concerns parents encounter in the early days home from the hospital. While the yellow color can look alarming, most newborn jaundice is normal and resolves without treatment. Knowing what to look for and when to act makes a big difference.
What Causes Newborn Jaundice
Jaundice is caused by a buildup of bilirubin — a yellow pigment produced when red blood cells break down. Newborns have a relatively high number of red blood cells at birth (which they don't need as much of once they can breathe air), and these cells break down faster than their immature livers can process the resulting bilirubin. The bilirubin accumulates in the body's tissues, causing the yellow discoloration.
This type is called physiological jaundice — it's a normal part of the newborn transition, not a sign of illness. It typically appears between day 2 and day 4 after birth and usually resolves within 1–2 weeks in full-term babies (a bit longer in preemies).
Types of Jaundice
Physiological (normal) jaundice
The most common type. Appears after day 2, peaks around day 3–5, and gradually fades. Bilirubin levels stay within safe ranges and resolve without treatment in most cases.
Breastfeeding jaundice
Occurs in the first week when a baby isn't getting enough breast milk — whether because milk hasn't fully come in yet or because of latch or supply issues. Insufficient feeding means insufficient gut motility, which means bilirubin isn't being eliminated through stool fast enough. The treatment is increasing feeding frequency and effectiveness, often with lactation support.
Breast milk jaundice
A distinct and less-understood condition where a substance in breast milk slows bilirubin processing. It appears after week 1, peaks around weeks 2–3, and can persist for weeks or months at low levels. It rarely requires treatment and is not a reason to stop breastfeeding.
Pathological jaundice
Jaundice that appears in the first 24 hours of life, rises very rapidly, or reaches very high levels can indicate an underlying condition — blood type incompatibility (Rh or ABO incompatibility), infection, or a metabolic disorder — that requires investigation and treatment. This type is different from normal newborn jaundice and is taken seriously from the start.
How Jaundice Is Detected and Monitored
In the hospital, bilirubin is often checked with a non-invasive skin meter and, when elevated, confirmed with a blood test. Pediatricians use established threshold charts (based on the baby's age in hours and risk factors) to determine whether treatment is needed. At your newborn's first checkup — typically 2–3 days after hospital discharge — bilirubin is often checked again.
At home, check for jaundice in good natural light. Jaundice typically progresses from head to toe as levels rise. A yellow tint on the face and upper chest, or in the whites of the eyes, warrants a call to your pediatrician. Yellow color progressing to the belly, arms, and legs indicates higher levels.
Treatment: Phototherapy
When bilirubin reaches concerning levels, phototherapy (light treatment) is used. Special blue-spectrum lights break down bilirubin in the skin into a form that can be excreted without liver processing. Phototherapy is highly effective and safe. It may be done in the hospital or with a portable bili blanket at home. During treatment, feeding frequency is often increased (to help clear bilirubin through stool), and the baby's eyes are protected with small goggles.
When to Call Your Provider
Contact your pediatrician promptly if your baby looks increasingly yellow after going home, the yellow color reaches the belly or below, your baby seems very lethargic or difficult to wake for feeds, their urine is dark yellow or their stools are pale/white (which can indicate liver problems), or if you're at all concerned. Untreated very high bilirubin is rare but can cause hearing loss and, in severe cases, brain injury — which is why monitoring matters.
In the vast majority of cases, newborn jaundice is temporary and harmless. But it's worth watching carefully, particularly in the first two weeks.
Sources & Further Reading
Understanding Newborn Jaundice: When to Watch and When to Worry
Newborn jaundice (hyperbilirubinemia) is one of the most common conditions in the first week of life, affecting 60% of full-term newborns and up to 80% of preterm babies. The yellow skin tone that characterizes jaundice can be alarming to new parents — but in most cases, it's a normal physiological process that resolves without treatment. Understanding what's normal, what's not, and what the treatment involves helps you advocate effectively for your baby.
What Causes Jaundice in Newborns
Jaundice is caused by elevated bilirubin — a yellow pigment produced when red blood cells break down. Before birth, the placenta handles bilirubin processing. After birth, the newborn liver takes over, but it's initially immature and slow to process the high volume of bilirubin from the rapid breakdown of fetal red blood cells (which are different from adult red blood cells and break down quickly after birth). The backlog of unprocessed bilirubin deposits in the skin and whites of the eyes, causing the yellow tinge.
Types of Newborn Jaundice
| Type | When It Appears | Duration | Concern Level |
|---|---|---|---|
| Physiological (normal) | Days 2–4 | Resolves by 1–2 weeks | Low — monitor at home |
| Breastfeeding jaundice | Days 2–5 | Resolves with feeding improvement | Low-moderate — optimize feeding frequency |
| Breast milk jaundice | Days 4–7 | Can persist 3–12 weeks | Usually benign; monitor bilirubin levels |
| Pathological | Within 24 hours of birth | Requires treatment | High — immediate evaluation |
How to Check for Jaundice at Home
Jaundice progresses from head to feet as bilirubin levels rise. In natural light (not fluorescent), press gently on your baby's forehead or nose — if the skin looks yellow when you release pressure, jaundice is present. Check the whites of the eyes as well. Yellow discoloration moving below the belly button warrants a same-day call to your pediatrician.
Home assessment is a rough screen only — bilirubin levels must be measured by a blood test or transcutaneous bilirubinometer (non-invasive forehead scanner) for any treatment decision. Don't rely on visual assessment alone if you're concerned.
Treatment: Phototherapy
When bilirubin reaches treatment thresholds (which vary by age in hours and gestational age), phototherapy is the standard treatment. Blue-spectrum light breaks down bilirubin in the skin into water-soluble forms the baby can excrete in urine and stool. Phototherapy is safe, effective, and typically works within 24–48 hours.
Hospital phototherapy uses a light "bili bed" or overhead lights. Home phototherapy (a "biliblanket") is sometimes used for lower-risk cases. During phototherapy, feeding frequently is critical — bilirubin is excreted in stool, so more feeds = more bowel movements = faster resolution. Phototherapy is not sunlight exposure; regular window sunlight is neither safe (UV risk) nor effective.
Warning Signs That Need Immediate Attention
While most jaundice is benign, very high bilirubin levels can cause kernicterus — brain damage that is permanent but preventable with timely treatment. Call your provider or go to the ER immediately if your jaundiced baby shows:
- High-pitched crying or inconsolable crying
- Extreme limpness or stiffness
- Difficulty waking or feeding
- Jaundice appearing within the first 24 hours of life
- Yellowing spreading below the navel, into arms and legs
- Yellow tint to the whites of the eyes
Kernicterus is rare in the US because jaundice screening is standard before hospital discharge. The system works when parents and providers both follow up appropriately after discharge.
Frequently Asked Questions
Should I stop breastfeeding if my baby has jaundice?
In most cases, no. The AAP recommends continuing breastfeeding and increasing feeding frequency (8–12 times per 24 hours) as the first-line approach for breastfeeding-associated jaundice. More feeds means more bowel movements and faster bilirubin clearance. Temporary formula supplementation may be recommended if bilirubin is approaching treatment thresholds and feeding is inadequate — but this is a decision made with your provider, not a default first step.
Does putting a jaundiced baby in sunlight help?
The light wavelength that breaks down bilirubin is in the blue-green spectrum; ordinary sunlight has the wrong spectrum and carries UV exposure risk for newborn skin. Indirect sunlight through a window is not an effective treatment and is not recommended by the AAP as a substitute for medical phototherapy. If your baby needs treatment, medical-grade phototherapy is the evidence-based approach.
My 3-week-old still looks a little yellow. Is that normal?
Breast milk jaundice can persist for 3–12 weeks in some breastfed babies and is usually benign. However, jaundice persisting beyond 2 weeks should always be evaluated by your pediatrician — not to alarm you, but because prolonged jaundice can occasionally be caused by conditions (like hypothyroidism or biliary atresia) that need treatment. A quick bilirubin check and a few other labs can rule out any underlying cause.