Hemolytic disease of the fetus and newborn (HDFN) caused by ABO incompatibility between the mother and her baby is more common and often causes less severe symptoms than HDFN caused by incompatibility of the RhRh factor A protein or antigen found on red blood cells. When an Rh-negative mother carries an Rh-positive fetus, her immune system may make antibodies that attack the fetus' red blood cells. blood groupBlood group A classification of blood based on inherited markers found on red blood cells. The ABO and Rh blood groups are most common in HDFN..
ABO incompatibility in HDFN can also decrease the risk of sensitizationSensitization The process by which a mother’s immune system becomes “primed” to recognize and attack fetal red blood cells carrying incompatible antigens. to other red blood cell antibodiesAntibody A protein made by the immune system that recognizes and attacks foreign substances, such as bacteria, or in HDFN, fetal red blood cells carrying incompatible antigens., including anti-D, anti-c or anti-Kell.
What is HDFN?
Hemolytic disease of the fetus and newborn (HDFN) is an immune-mediated red blood cell disorder that occurs when a baby’s RBCs break down quickly, which is called hemolysis. HDFN is caused by a mismatch between a mother’s and her baby’s blood type (A, B, AB, or O) or Rhesus (Rh) factor (Rh-positiveRh-Positive A blood type trait that means your red blood cells have the Rh(D) antigen. or Rh-negativeRh-Negative A blood type trait that means your red blood cells lack the Rh(D) antigen.) during pregnancy.
What is ABO incompatibility in HDFN?
ABO incompatibility occurs when a mother has the 0 blood type and her baby’s blood type is A or B. This can lead to HDFN, where the mother’s immune system develops antibodies that cross the placenta and attack the fetus’s red blood cells, progressively breaking them down.
While ABO incompatibility occurs in about 15% to 20% of pregnancies, only about 1% of these pregnancies develop HDFN. It doesn’t generally lead to problems during pregnancy, and following delivery symptoms can range from mild to moderate.
In ABO incompatibility, the newborn usually experiences jaundiceJaundice A common symptom of HDFN, jaundice is caused by excess bilirubin and is characterized by a yellow tint to the skin or eyes. and in some cases, anemiaAnemia A condition that occurs when the body doesn’t have enough healthy red blood cells to carry oxygen to its tissues. In HDFN, anemia occurs when maternal antibodies destroy fetal red blood cells.. Symptoms are often successfully treated with phototherapyPhototherapy A treatment that uses special blue light to help newborns break down bilirubin and prevent kernicterus., and only in rare cases does it lead to severe symptoms that require treatment by blood transfusions, exchange transfusions or intravenous immunoglobulinIntravenous immunoglobulin A therapy made from donated antibodies that may help reduce the mother’s immune response and protect the fetus..
Learn more about HDFN causes and risk factors
Protective effect of ABO incompatibility
Cases of ABO incompatibility-related HDFN have the protective effect of helping to prevent maternal sensitization to the RhD antigen, as well as anti-c and anti-Kell. This is due to maternal anti-A or anti-B antibodies attacking the fetal red blood cells early in pregnancy, before other red cell antigensAntibody A protein made by the immune system that recognizes and attacks foreign substances, such as bacteria, or in HDFN, fetal red blood cells carrying incompatible antigens. can be detected. Fetal red blood cells that come into contact with maternal blood cells are quickly destroyed, which reduces the risk of maternal sensitization to the D, c and Kell antigens.
Managing ABO incompatible pregnancies
The possible incompatibility of blood types between mother and baby can be predicted with ABO blood typing during prenatal testing. If ABO incompatibility is flagged as a potential risk during pregnancy, regular monitoring will be essential to ensure early intervention and adequate prenatal care management if the fetus develops HDFN and demonstrates symptoms of anemia.
Following delivery, the newborn may also require close monitoring and follow-up care to manage signs of jaundice or anemia proactively. Outcomes in ABO incompatible pregnancies are usually positive, but complications can occur in some cases.
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