At what level does pathological jaundice occur due to ABO/Rh incompatibility?

Pathological jaundice due to ABO or Rh incompatibility typically presents within the first 24 hours after birth, which is why day 1 is the correct answer. In cases of hemolytic disease caused by ABO incompatibility, the breakdown of red blood cells leads to the release of bilirubin, resulting in jaundice that can start almost immediately after birth. The elevation of bilirubin levels can occur rapidly due to the incompatibility between the mother's blood type and that of the infant, which is why it is a crucial observation in the early hours of life.

While jaundice can occur later on due to other factors or conditions, such as physiological jaundice, which usually manifests after 24 hours, hypoxia, or situations in which other underlying issues present, those situations are distinct from ABO/Rh incompatibility that clearly causes jaundice starting at birth or on day 1 specifically. Thus, day 1 accurately reflects the timing of pathological jaundice in the context of ABO/Rh incompatibility.