HDN

Notes (Disclaimer: I am not a doctor or expert in anatomy)

Red Blood Cells (Erythrocytes) of a New Born Infant or Perinatal Fetus are destroyed prematurely resulting in Anemia.

Happens when blood types of Mother and Baby are incompatible.

A Blood type is dependent upon certain Antigens that are either present or absent.

Incompatibility happens when the Baby has an antigen that the Mother does not have. The Mother’s immune system interprets the antigen as foreign and thus produces antibodies to target the cells carrying the antigen for destruction. While in principle it can happen between a mismatch in any blood group, severe cases most commonly occur with mismatch in the D antigen of the Rh System. Hemolytic Disease of the Newborn (HDN) can occur when the Mother’s blood has blood with no D antigen and the New Born has blood with a D antigen.

The first pregnancy is usually not at risk. This is because the placenta normally does a good job separating the Mother’s blood from the Fetal blood. Thus preventing the Fetal blood from being exposed to the Mother’s immune system.

In the cases of Birth, Miscarriage, and Abortion the tearing of the placenta can expose the Mother’s blood to Fetal blood thus causing antibodies to be produced by the Mother. Antibody production takes sometime so it does not affect the first baby.

If the Mother becomes pregnant with another Rh+ (has the D-antigen), the Mother’s blood now has the antibodies and HDN may occur. The antibodies able to cross the placenta can now cause hemolysis.

Blood transfusions, Sharing Needles, or Medical Procedures can lead to the antibody being present in the first pregnancy.

Anemia can cause Heart Failure, Respiratory Distress, and Edema.

Infants with HDN can develop Anemia.

Infants with HDN can develop Brain Damage (kernicterus) due to bilirubin being toxic to brain tissue.

Infants with HDN can develop Jaundice (due to accumulation bilirubin, a yellow product of hemoglobin breakdown). Levels rise quickly within 24 hours of birth.

Other signs include enlarged liver, enlarged spleen, erythroblasts (immature red blood cells, erythroblastosis fetalis) in the blood.

HDN that involves D-antigen can be effectively prevented with Anti-D antibody. It is given during and soon after the first mismatched pregnancy.

Some signs can be detected before birth with ultrasound imaging.

Infants born with HDN are usually treated with intravenous fluid and phototherapy. Phototherapy uses a specific spectrum of light to break down bilirubin into a product easier for the infants body to excrete.

The Infant anemia may be treated with blood transfusion.