Makindo Medical Notes

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About Haemolytic Disease of the Newborn

• A condition caused by haemolysis within the fetus due to the passage of maternal antibodies against the Rhesus (Rh) antigen.
• Occasionally seen due to incompatibilities between less common fetal and maternal blood group antigens, though Rhesus incompatibility is the most common cause.

Aetiology

• Occurs in Rhesus-negative mothers previously exposed to Rh-positive blood, leading to antibody formation. Exposure can happen during a prior pregnancy with an Rh-positive fetus or through transfusion of Rh-positive blood.
• Upon re-exposure, such as in a subsequent pregnancy with an Rh-positive fetus, maternal antibodies cross the placenta and cause fetal haemolysis.

Clinical Features

• Jaundice: Typically occurs soon after birth due to elevated bilirubin from RBC breakdown.
• Severe Hyperbilirubinaemia: Excessive bilirubin levels can lead to neurological complications.
• Severe Anaemia: Results from the destruction of fetal RBCs.
• Kernicterus: Severe neurological damage due to bilirubin accumulation in the brain.
• Hydrops Fetalis: Severe form leading to fetal death, characterized by generalized edema.

Investigations

• Blood Type Testing: Determine if the fetus is Rhesus-positive, placing an Rh-negative mother at risk.
• Coombs Test (Direct Antiglobulin Test): Positive test indicates antibody-coated RBCs in the fetus.
• Red Blood Cell Count: Decreased RBC count due to haemolysis.
• Reticulocytosis: Elevated immature RBCs as the body attempts to compensate for anaemia.
• Macrocytosis: Larger RBCs seen due to increased reticulocytes.
• Polychromasia: Presence of RBCs of varying colors indicating reticulocytosis and active haemolysis.
• Microspherocytosis: Small, spherical RBCs, a hallmark of haemolytic anaemia.

Management

• Transfusion: May be necessary in severe cases to correct anaemia.
• Hydration: Helps support circulation and bilirubin clearance.
• Phototherapy: A safe and effective treatment for reducing bilirubin levels by converting it to a form excretable by the body.
• Exchange Transfusion: In severe cases, exchange transfusion can remove bilirubin and antibody-coated RBCs, reducing haemolysis and bilirubin levels.

Prevention

• Rhesus-negative mothers should receive Anti-D immunoglobulin (Anti-RhD) whenever there is a risk of fetal blood exposure (e.g., miscarriage, delivery, or procedures that may cause fetal-maternal blood mixing).
• Administer Anti-D following delivery to prevent maternal sensitization, reducing the risk of antibody response in future pregnancies.

Administering Anti-D immunoglobulin helps prevent maternal immune system activation against the Rhesus antigen in future pregnancies, thus reducing the risk of haemolytic disease in subsequent Rh-positive fetuses.