Newborn jaundice is one of the most common conditions in the first week of life — affecting approximately 60% of full-term newborns and up to 80% of premature babies. For most families, it's detected at the first pediatric checkup, monitored for a few days, and resolves without treatment. For some babies, it requires phototherapy. Here's everything parents need to understand about jaundice: what it is, why it happens, how it's monitored, and when it warrants concern.
What Is Newborn Jaundice?
Jaundice is a yellowing of the skin and whites of the eyes caused by elevated levels of bilirubin in the blood. Bilirubin is a yellow pigment produced when red blood cells break down. In adults and older children, the liver efficiently processes and excretes bilirubin. In newborns, the liver is still immature and can't keep up with the initial bilirubin load — particularly because newborns have extra red blood cells that break down rapidly after birth as the body transitions from fetal to newborn circulation.
The result: bilirubin accumulates in the blood and deposits in the skin and eyes, producing the characteristic yellow tint.
Types of Newborn Jaundice
Physiological Jaundice (Most Common)
The normal, expected jaundice that affects the majority of newborns. It appears on day 2–3 of life (never on day 1), peaks around day 4–5, and typically resolves by 2 weeks in full-term babies and 3 weeks in premature babies. It requires monitoring but usually no treatment.
Breastfeeding Jaundice
Occurs in the first week when a baby is not feeding well — insufficient milk intake means less bilirubin is excreted through the stool. The solution is improving feeding frequency and effectiveness, not stopping breastfeeding. A lactation consultant referral is often appropriate if this type is identified.
Breast Milk Jaundice
A distinct condition from breastfeeding jaundice. Occurs in 2–3% of breastfed babies, typically appearing after day 5 and persisting for several weeks. Caused by substances in breast milk that inhibit bilirubin excretion. Usually mild, rarely requires treatment, and resolves on its own. Does not require stopping breastfeeding.
Pathological Jaundice
Jaundice that appears in the first 24 hours of life, rises very rapidly, or reaches very high levels. Can be caused by blood group incompatibility (Rh or ABO), G6PD deficiency, infection, or structural liver problems. Always requires medical evaluation and often treatment.
Recognizing Jaundice
The yellow color of jaundice appears first on the face, then progresses downward to the chest, abdomen, arms, and finally legs and feet as bilirubin levels rise. A useful home assessment: in good natural light, gently press a finger to baby's forehead or nose and release — if the skin underneath looks yellow rather than pink or beige, jaundice is likely present.
This visual assessment gives an approximate sense of jaundice level but is not accurate enough to replace measurement. Jaundice in darker-skinned babies may be harder to see in the skin but should be visible in the whites of the eyes.
How Bilirubin Is Measured
Two main methods:
- Transcutaneous bilirubinometry (TcB): A non-invasive device placed on the skin that estimates bilirubin level optically. Used for screening.
- Serum bilirubin (blood test): A small blood sample from the heel, providing an accurate measurement. Used when TcB levels are elevated or when the baby has risk factors.
Results are interpreted using a nomogram — a chart that plots the bilirubin level against the baby's age in hours and identifies whether the level is low risk, intermediate risk, or high risk requiring treatment. The threshold for treatment is not a single number; it depends on age in hours and gestational age.
Treatment: Phototherapy
When bilirubin reaches the treatment threshold, phototherapy ("bili lights") is the standard treatment. Blue-green light at specific wavelengths (420–490nm) converts bilirubin in the skin into a form that can be excreted without liver processing. It's safe, effective, and has been the standard treatment for jaundice since the 1960s.
During phototherapy:
- Baby is placed under the light source with eyes protected by small goggles
- Maximum skin exposure is maintained — minimal clothing
- Feeding continues normally and frequently (at least every 2–3 hours) to promote bilirubin excretion
- Bilirubin is monitored with blood tests every 4–12 hours
- Most babies respond within 12–24 hours
Home phototherapy with a bili blanket (a fiber-optic blanket that wraps around the baby) is available for mild to moderate jaundice and allows treatment at home with monitoring.
What Doesn’t Work
- Sunlight through windows: Window glass filters out the UV wavelengths needed for phototherapy. Indoor light through windows does not treat jaundice.
- Placing baby in a sunlit window: Recommended in older guidelines but not effective through glass, and carries a risk of sunburn. Not a substitute for medical phototherapy.
- Stopping breastfeeding: Rarely indicated; in most cases reduces feeding frequency, which worsens bilirubin clearance.
When to Contact Your Pediatrician
- Jaundice appears in the first 24 hours of life — always requires same-day evaluation
- Yellowing spreads below the navel
- Baby is very difficult to rouse, feeding poorly, or making a high-pitched cry
- Jaundice appears to be worsening after day 5
- Jaundice has not resolved by 3 weeks in a full-term baby
- Yellow color appears in the whites of the eyes along with pale or clay-colored stools and dark urine — this suggests a different type of jaundice requiring urgent evaluation
Why Frequent Feeding Matters
Bilirubin is excreted primarily through the stool. Frequent feeding — at least 8–12 times per 24 hours in the first days — promotes bowel movements and therefore bilirubin clearance. This is one of the most important things parents can do at home. Well-fed babies with good stool frequency have lower peak bilirubin levels and shorter jaundice courses than underfed babies.
For feeding frequency guidance in the first weeks, see our newborn feeding schedule guide and our breastfeeding positions guide if latch and milk transfer are concerns.