The incidence of alloimmunization, the determinant condition involved in hemolytic disease of the fetus and newborn (HDFN), appears to vary greatly among different populations, ethnic group, as well as the method used to detect it according to a recently published HDFN literature review in Cureus.
What is HDFN?
Hemolytic disease of the fetus and newborn (HDFN) is an immune-mediated red blood cell (RBC) 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-positive or Rh-negative) during pregnancy. Numerous antibodies to RBC antigens can be linked to HDFN, such as those from the ABO and Rh blood group systems.
Alloimmunization is the process by which the body produces antibodies that target a molecule present in the body of another human; this target is known as an antigen.
The most common form of alloimmunization is the one that occurs against antigens present in red blood cells (RBC) in the context of emergency blood transfusions or pregnancies in which the mother has a different blood type than the fetus. During pregnancy, these antibodies can cross the placental barrier and cause HDFN.
Learn more about HDFN causes and risk factors
Recent statistics suggest that approximately 0.45% and 2.4% of the global population is alloimmunized against a RBC antigen. The most frequent cause of RBC alloimmunization is pregnancy followed by blood transfusions. Patients with chronic forms of anemia such as sickle cell disease and thalassemia are considered to be at higher risk of alloimmunization as they can require several transfusions through their lifetime.
As the frequency of RBC antigens changes among different populations and ethnic groups, there is great variability in the incidence of alloimmunization depending on the population.
“In Asian countries, antibodies toward Rhesus antigen showed the highest prevalence with anti-E and anti-D, respectively, while, among Caucasian, anti-K is the most common,” the authors wrote. “This means that individuals from different ethnic groups may be more or less likely to develop alloimmunization in response to exposure to certain antigens.”
Still, irrespective of ethnicity, anti-Rh D antigen antibodies appear to be the most frequent, making it the most common cause of HDFN. Therefore, most countries recommend RhD and ABO testing as an integral part of prenatal care.
“RBC alloimmunization during pregnancy is common, but this complication can have a negative impact on both mother and fetus,” the authors wrote. “Depending on the population investigated and the screening techniques used, the frequency of RBC alloimmunization in pregnancy can vary considerably.”
