What are the characteristics of pathological jaundice?

Generally speaking, the first criterion is early onset of jaundice: in term infants, jaundice appears within 24 hours after birth; in preterm infants, it appears within 48 hours after birth—this indicates an unusually early onset.

Second, the jaundice is severe: serum bilirubin levels exceed the average for age-matched healthy infants—i.e., ≥220 μmol/L (≥12.9 mg/dL) in term infants or ≥256 μmol/L (≥15 mg/dL) in preterm infants. In addition to facial and truncal jaundice, obvious yellow discoloration extends to the lower legs, forearms, palms, and soles—indicating a high degree of jaundice.

Third, prolonged duration of jaundice: typically, jaundice persisting beyond two weeks in term infants or beyond four weeks in preterm infants—or jaundice that resolves and then reappears or worsens—is considered a hallmark of pathological jaundice.

Fourth, rapid progression of jaundice: a marked increase in intensity within one day, or a daily rise in serum bilirubin exceeding 85.5 μmol/L (5 mg/dL), suggests pathological jaundice.

Fifth, late-onset jaundice: jaundice appearing one week or more after birth—often emerging several weeks postnatally—is also classified as pathological jaundice.

Sixth, elevated direct (conjugated) bilirubin: serum direct bilirubin exceeding 25 μmol/L (1.5 mg/dL) is indicative of pathological jaundice.