What is the primary consequence of HDN for the fetus?

• A. Destruction of fetal red blood cells
• B. Cerebral hemorrhage
• C. Increased fetal growth
• D. Improved oxygen delivery

Answer: (A)

Destruction of fetal red blood cells due to maternal antibodies crossing the placenta. In HDN, maternal anti-Rh or other antibodies target fetal RBCs, causing hemolysis. The immediate and primary consequence for the fetus is anemia from the loss of red cells, which reduces oxygen-carrying capacity. The fetus responds by increasing erythropoiesis, but extensive hemolysis can lead to complications such as hydrops fetalis and hyperbilirubinemia after birth, which can cause jaundice and, if severe, neurological damage. The other options don’t reflect the main effect: HDN does not cause increased growth or improved oxygen delivery; instead, it diminishes oxygen delivery due to anemia.