Which condition is the most likely cause of jaundice in a group A, Rh-positive infant born to an O, Rh-positive mother?

Jaundice in a newborn can arise from various factors, but in the scenario described—an A, Rh-positive infant born to an O, Rh-positive mother—ABO incompatibility is the most probable cause. This condition occurs when a mother with blood type O has antibodies against A and B antigens, which can cross the placenta and react with the A antigen present on the red blood cells of an A-type infant.

In this case, the mother's type O blood contains anti-A antibodies that may attack the red blood cells of her type A infant, resulting in hemolysis. This breakdown of red blood cells leads to an increase in bilirubin levels, causing jaundice. ABO hemolytic disease tends to be less severe than Rh incompatibility but remains a significant cause of jaundice in newborns.

Rh incompatibility, on the other hand, would typically occur when an Rh-negative mother has formed antibodies against Rh-positive red blood cells after a previous pregnancy or transfusion. Since the mother is Rh-positive in this scenario, Rh incompatibility is not a concern.

The possibility of blood group incompatibility due to antibodies against low-frequency antigens is relatively rare and less likely to be a significant factor in this situation. Neonatal jaundice that is