A term baby developed jaundice on 3rd day up to the thigh with normal stool and urine. Mother’s blood group is ‘O’ –ve and that of babies ‘A’ +ve. The cause of jaundice is –
**Core Concept**
The question is testing the understanding of the pathophysiology of hemolytic disease of the newborn (HDN) due to ABO incompatibility. This condition occurs when the mother has antibodies against the ABO blood group antigens present on the baby's red blood cells, leading to their destruction.
**Why the Correct Answer is Right**
The mother's 'O' negative blood group contains anti-A and anti-B antibodies, which are naturally present in her plasma. Since the baby has an 'A' positive blood group, the mother's antibodies will react with the A antigens on the baby's red blood cells, marking them for destruction. This leads to hemolysis, resulting in jaundice. The presence of normal stool and urine suggests that the jaundice is not due to a bile duct obstruction or liver dysfunction.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not account for the mother's blood group and the presence of anti-A antibodies.
**Option B:** This option is incorrect as it does not explain the mechanism of hemolysis due to ABO incompatibility.
**Option C:** This option is incorrect as it is unrelated to the ABO blood group system and the pathophysiology of HDN.
**Clinical Pearl / High-Yield Fact**
In cases of suspected HDN due to ABO incompatibility, it is essential to perform a cross-match test to determine the presence of maternal antibodies against the baby's red blood cells. This can help guide the management and prevent further hemolysis.
**Correct Answer: A. ABO incompatibility between the mother's 'O' negative blood group and the baby's 'A' positive blood group is the cause of jaundice.**