Hemolytic Disease of the Newborn (HDN) occurs when a mother's immune system attacks her baby's red blood cells. This usually happens when the mother has a different blood type than the baby, particularly involving the Rh factor. If the mother is Rh-negative and the baby is Rh-positive, the mother's body may produce antibodies that can cross the placenta and destroy the baby's red blood cells. Symptoms of HDN can include jaundice, anemia, and swelling in the baby. Treatment options may involve blood transfusions or phototherapy to reduce bilirubin levels. Early detection and management are crucial to prevent serious complications for the newborn.