Newborn Jaundice: Causes, When It Peaks, and When to Act

What Is Newborn Jaundice?

Jaundice is a yellow tint to the skin and the whites of the eyes caused by elevated bilirubin — a yellow pigment produced during the normal breakdown of red blood cells. It's one of the most common conditions in newborns: approximately 60% of full-term babies and up to 80% of premature babies develop visible jaundice in the first week of life.

In newborns, the yellow appearance typically starts at the head and face and progresses downward as bilirubin levels rise — useful information for monitoring at home between clinic visits.

The two main reasons newborns are prone to jaundice:

• Fetal red blood cells are broken down rapidly after birth — newborns have more red blood cells than adults, and they break down faster
• Immature liver — the newborn liver is still developing its capacity to process and excrete bilirubin efficiently

Physiological jaundice is not contagious, not caused by anything a parent did, and in most cases resolves without medical treatment.

Normal Timeline: When It Peaks and When It Clears

Understanding the different types of newborn jaundice helps you know what to expect:

• Physiological jaundice — appears day 2–3 of life (not before), peaks day 3–5, and typically resolves by 2 weeks in full-term babies. This is the most common type.
• Premature babies — jaundice tends to be more pronounced and can last 2–3 weeks due to a more immature liver
• Breastfeeding jaundice — occurs in the first week when breastfeeding is not yet well established and intake is low. Inadequate feeding means fewer stools, and bilirubin is excreted primarily through stool. The fix: feed more frequently.
• Breast milk jaundice — a distinct condition appearing in week 2–3, after feeding is well established, caused by substances in breast milk that affect bilirubin processing. Can last up to 6 weeks. Entirely benign — breastfeeding should continue.

The key distinction: breastfeeding jaundice (early, due to low intake) vs. breast milk jaundice (late, due to breast milk composition). The former is more concerning; the latter is almost always harmless.

What Helps at Home

For physiological and breastfeeding jaundice, the most effective intervention parents can do is straightforward:

• Feed frequently — this is the most important step. Every 2–3 hours during the day and at least every 4 hours at night. More feeding = more stool = more bilirubin excreted. Waking a sleepy jaundiced baby to feed is appropriate and necessary.
• Breastfeeding support — if latch or supply is a concern, get help from a lactation consultant early. Low intake is the most fixable cause of early jaundice. See our breastfeeding guide for latch and supply information.
• Sunlight through a window — filtered, indirect sunlight may provide mild support. Never put a newborn in direct sunlight — they can burn in minutes. Sunlight through glass removes the UV component needed for bilirubin breakdown, so its effect is limited. It is not a substitute for medical assessment.

Phototherapy: When It's Needed

When bilirubin levels exceed the threshold on an age-based nomogram (a chart that plots bilirubin level against the baby's age in hours), phototherapy is recommended. The threshold varies depending on gestational age, risk factors, and how old the baby is in hours — there is no single universal number.

Phototherapy works by using blue-wavelength light to break bilirubin down into water-soluble forms that can be excreted without liver processing. The baby lies under special lights (or on a light-emitting blanket) with eyes protected. It is painless and highly effective.

• Conventional phototherapy takes place in hospital, with baby in a crib under lights
• Home phototherapy (bili blanket) may be available in some regions for lower-risk cases
• Breastfeeding should continue during phototherapy — feeds are the primary bilirubin excretion route

Do not delay seeking assessment to "wait and see" if you are concerned. High bilirubin that could have been treated with phototherapy becomes a medical emergency when treatment is delayed.

When to Seek Urgent Care

Most jaundice is physiological and manageable. Seek same-day or urgent medical care if you notice:

• Jaundice in the first 24 hours of life — this is always pathological and requires urgent evaluation. It may indicate hemolytic disease (Rh incompatibility or ABO incompatibility) where red blood cells are being destroyed rapidly.
• Rapidly deepening yellow color — yellow spreading quickly to the arms, legs, and palms/soles of feet
• Baby is extremely sleepy and difficult to wake — excessive sleepiness in a jaundiced newborn is a warning sign
• Refusing to feed — a jaundiced baby who won't feed needs urgent assessment
• Fever or signs of infection alongside jaundice — see our fever guide
• High-pitched cry — can indicate bilirubin toxicity affecting the brain

Never discharge from hospital or clinic without a plan for bilirubin follow-up. The standard recommendation is a bilirubin check within 24–48 hours after discharge for all jaundiced newborns.