Which statement is true about ABO incompatibility?

Which statement is true about ABO incompatibility?

• A. Mom is O and fetus is A, B, or AB; anti-A or anti-B antibodies can cause hemolytic disease of the newborn
• B. Mom is AB and fetus is O; antibodies cause disease
• C. ABO incompatibility only occurs in Rh-positive mothers
• D. ABO incompatibility never causes hemolysis

Answer: (A)

ABO incompatibility occurs when maternal anti-A and anti-B antibodies cross the placenta and attack fetal red blood cells that express A, B, or AB antigens. A type O mother has these antibodies, and if the fetus inherits A, B, or AB antigens, the IgG antibodies can cross to the fetus and cause hemolysis, leading to fetal anemia and newborn jaundice or hyperbilirubinemia. This can happen regardless of the fetus’s Rh status, though the condition is usually milder than Rh incompatibility. The other scenarios don’t fit: a mother with type AB lacks anti-A and anti-B antibodies to attack a type O fetus; ABO incompatibility is not limited to Rh-positive mothers; and it can indeed cause hemolysis, not never.

ABO incompatibility occurs when maternal anti-A and anti-B antibodies cross the placenta and attack fetal red blood cells that express A, B, or AB antigens. A type O mother has these antibodies, and if the fetus inherits A, B, or AB antigens, the IgG antibodies can cross to the fetus and cause hemolysis, leading to fetal anemia and newborn jaundice or hyperbilirubinemia. This can happen regardless of the fetus’s Rh status, though the condition is usually milder than Rh incompatibility.

The other scenarios don’t fit: a mother with type AB lacks anti-A and anti-B antibodies to attack a type O fetus; ABO incompatibility is not limited to Rh-positive mothers; and it can indeed cause hemolysis, not never.