A case report involving a case of hemolytic disease of the fetus and newborn (HDFN) in an AB blood type newborn due to A1 alloantibodies has been recently published in Blood and Genomics.
A person’s blood type is determined by certain molecules (antigens) present on the surface of their red blood cells (RBCs). There is a great variety of RBCs antigens, such as A, and B antigens, that determine the ABO type, the RH antigen, and the Kell antigen. When a person is said to be A +, that means that they have A and Rh antigens present on the surface of their RBCs.
In a pregnancy in which the fetus has an antigen absent in the RBCs of the mother, the maternal immune system can develop antibodies against these antigens. In a future pregnancy, these antibodies can cross the placenta and destroy fetal RBCs, causing HDFN.
Learn more about HDFN causes and risk factors
Not all antigens have the same potential to produce a strong immune response that results in HDFN; RH antigen is particularly immunogenic, which means it can produce a strong immune response capable of producing HDFN. A and B antigens, on the other hand, do not tend to produce such a strong response. The great majority of cases of HDFN due to ABO incompatibility occur in type O mothers, cases in which the mother is either A or B are extremely rare.
“ABO incompatibility between mother and fetus appears in 20% of all pregnancies, while 1%–4% of newborns develop HDN,” the authors wrote.
The authors described an HDFN case in which the mother was B-positive and the fetus AB-positive. The premature infant was admitted to the hospital due to severe anemia manifested through extreme paleness and shortness of breath.
The patient and his parents were tested for blood type, and initial tests revealed him to be AB-positive and the mother to be B positive. However, more extensive testing revealed that the mother had antibodies directed towards the A1 antigen, a subtype of the A antigen. After undergoing blood transfusions and phototherapy, the patient was discharged with satisfactory evolution.
“Future research focuses on improving the sensitivity of the test to promote the timely identification of the presence of fetal blood in maternal circulation so as to predict FMH and HDN,” the authors concluded.
