December 27, 2024

Katelyn Tran

11th Grade

Fountain Valley High School

Erythroblastosis fetalis, or hemolytic disease of the fetus and newborn (HDFN), is a potential pregnancy complication resulting from differences in blood type between a mother and her fetus. When newborns have blood cells that contain antigens that their mothers’ red blood cells do not, high contact with the fetus’s blood provokes an immune response in the mother’s body because her immune system perceives the antigens as a foreign threat, responding with the production of antibodies. This triggering exposure is called a sensitizing event. 

After an initial sensitizing event, a mother’s immune system becomes accustomed to recognizing such antigens and already has antibodies produced to attack cells that possess them. For this reason, if mothers become or are pregnant after a sensitizing event, the antibodies from their immune system may attack the fetus’s red blood cells if they contain the corresponding antigen. In general, HDFN less frequently affects firstborns because one of the most common sensitizing events is the delivery of a child with a different blood type. In this case, the immune response caused by the mother’s immune system would have little effect on the firstborn child because the child is no longer inside of the mother’s womb, but it would still leave behind antibodies in the mother’s bloodstream. However, it is worth acknowledging that there are other means of sensitization aside from delivery, such as abdominal trauma or other obstetric complications.

Newborns affected by HDFN often exhibit symptoms such as jaundice, lethargy, or tachycardia, but other signs like hyperbilirubinemia (elevated levels of bilirubin, a waste product resulting from the destruction of red blood cells) or anemia can also suggest that a child has erythroblastosis fetalis. Most of the time, symptoms are resolved through blood transfusions or the provision of iron supplements depending on severity, but serious cases can require more advanced care. However, the prevalence of HDFN is generally very low due to effective prevention that has thus mitigated its occurrence.

The most common blood type difference that causes HDFN is an Rh-negative mother pregnant with an Rh-positive child. Rh-positive refers to the presence of Rhesus D antigens on the surface of red blood cells; because Rh-negative individuals lack these antigens, sensitizing events trigger an immune response with the production of antibodies that recognize and attack blood cells that have them. So, if an Rh-negative mother were to give birth to an Rh-positive child, her future children may be at risk of developing HDFN if they have that same blood type difference due to those antibodies. Because scientists have successfully identified the main blood types and sensitization events associated with HDFN, a means for preventative intervention has been developed: Rh immunoglobulin.

As part of prenatal care, mothers receive blood tests that identify their ABO blood type and the presence or absence of the Rhesus factor. From this, doctors can assess their risk of being affected by HDFN, proceeding with Anti-D prophylaxis prior to the occurrence of a sensitizing event. From 28 weeks into pregnancy to around 3 days after birth, a mother would receive injections of Rh immunoglobulin in order to prevent getting sensitized and eventually carrying a fetus that becomes affected by HDFN. These injections introduce passive Anti-D antibodies into the mother’s bloodstream, so when what would be a sensitizing event occurs, the body mistakenly perceives these antibodies as its own immune response. For this reason, the immune system does not create a response of its own under the impression that it already had. On the other hand, these antibodies do not actually attack cells with the Rhesus antigen, keeping fetuses today safe from erythroblastosis fetalis through low-risk and effective prevention.