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Neonatal hyperbilirubinemia, which results in jaundice, typically presents around 48-72 hours postpartum. This timing is significant as the newborn's liver is maturing and encountering the sudden demands of processing bilirubin, a byproduct of the breakdown of red blood cells.

During this period, physiological jaundice often occurs due to the increased production of bilirubin from red blood cell breakdown and the immature hepatic uptake and conjugation mechanisms in newborns. Jaundice that appears after the first 24 hours but before 72 hours is generally considered physiological, whereas jaundice that presents earlier than 24 hours or persists beyond this window could indicate pathological conditions.

By the time the infant reaches the 72-96 hour postpartum mark, bilirubin levels typically peak and begin to decrease if the jaundice is physiological. Jaundice that persists beyond the first week postpartum could also indicate other underlying conditions, making the timing of its presentation vital for the evaluation of the infant's health.