Blood Banking Technologist (BB ASCP) Practice Test 2026 – Comprehensive Exam Prep

Hemolytic disease of the newborn (HDN) primarily occurs when a Rh-negative mother generates antibodies against the Rh-positive red blood cells of her fetus. This situation typically arises during pregnancy or delivery when fetal blood cells (which are Rh-positive) enter the mother's bloodstream, usually during events such as delivery or trauma. Once these Rh-positive cells are recognized as foreign by the mother's immune system, the mother produces antibodies against them.

These antibodies can cross the placenta and enter the fetal circulation, leading to the destruction of fetal red blood cells, resulting in hemolysis. This condition can cause serious complications for the newborn, including anemia, jaundice, and in severe cases, heart failure or hydrops fetalis.

The other options do not accurately describe HDN: thickness of blood refers to conditions that are typically cardiovascular issues; fetal blood cell production failure pertains to hematological disorders; and infections during delivery relate to maternal-fetal transmission of pathogens, rather than immune responses to fetal blood cells. Thus, the formation of maternal antibodies against fetal Rh-positive red blood cells is fundamental to understanding hemolytic disease of the newborn.