Newborn Jaundice

A yellowing newborn on day 3 might be perfectly normal — or hours away from brain damage. The difference hinges on timing, bilirubin trajectory, and risk factors you must recognize.

Newborn jaundice results from elevated unconjugated (indirect) bilirubin due to rapid RBC breakdown combined with an immature liver that conjugates bilirubin slowly. Physiologic jaundice appears after 24 hours of life, peaks around days 3–5 in term newborns (days 5–7 in preterm), and resolves by 2 weeks. Total serum bilirubin (TSB) typically stays below 12 mg/dL in term infants. Pathologic jaundice appears within the first 24 hours, rises faster than 5 mg/dL per day, or exceeds age-specific thresholds on the Bhutani nomogram. Causes include ABO/Rh incompatibility, G6PD deficiency, cephalohematoma reabsorption, and breastfeeding difficulties reducing stool output. Untreated severe hyperbilirubinemia can cause kernicterus — bilirubin crosses the blood-brain barrier, depositing in the basal ganglia and causing irreversible neurological damage (high-pitched cry, opisthotonus, seizures). Phototherapy is first-line treatment: blue-green light (wavelength 460–490 nm) converts unconjugated bilirubin into water-soluble isomers excreted without liver conjugation. During phototherapy, you protect the eyes with opaque shields, expose maximum skin surface, monitor temperature, and increase feeding frequency to promote stooling. Exchange transfusion is reserved for critically elevated levels unresponsive to phototherapy.

Key Distinctions

Don't confuse physiologic jaundice (appears after 24 hours, self-limited) with pathologic jaundice (within 24 hours, rapidly rising, or persistent beyond 2 weeks) — jaundice in the first 24 hours is always pathologic and requires immediate workup. Breastfeeding jaundice (insufficient intake, days 2–5) differs from breast milk jaundice (substance in mature milk increasing enterohepatic circulation of bilirubin, after day 5–7, benign). Students confuse unconjugated (indirect, neurotoxic) with conjugated (direct, indicates liver disease) — NCLEX tests unconjugated.

Clinical Pearl

Yellow in 24 — never okay. Jaundice appearing before 24 hours is pathologic until proven otherwise. Think: first day, first alarm.