17. Heamolytic disease of the newborn

only covered in asynch and revision session

What are the 2 main mechanisms of Hameolytic disease of the newborn (RhD)?

• Antibody adsorption

• Foetal-maternal haemorrhage

What is haemolytic disease of the newborn?

RhD negative mother is pregnant with RhD positive baby

• In the first pregnancy blood mixing occurs

• Mother’s immune system exposed to RhD +ve cells and produces antibodies against them

• The child of the second pregnancy is affected by this

• IgG antibodies cross the placenta and bind to the babies erythrocytes

• These erythrocytes become coated in the antibodies

• Macrophages in baby’s spleen and liver phagocytoses the erythrocyte

FBC results of the baby with HDN

• Low Hb

• High reticulocytes

• High bilirubin

Blood film observations for HDN

• Nucleated RBCs

• Reticulocytes

• Spherocytes

• Acanthocytes

Symptoms of HDN

• Jaundice

• Splenomegaly

• Urine discolouration

Additional tests for HDN

• Anti-RhD antibody titre (mum)- this will be high in HDN

• +ve direct antibody test (Baby)

• Positive Kleihauer test (Mum)

  • Measures ratio of foetal RBCs in the mothers blood stream

How is HDN prevented in the UK

• RhD negative mother given a drug RhoGAM

• This clears foetal cells from mothers circulation

• Works by binding to any foetal cells before the mothers immune system detects them and forms antibodies against them

Treatment of HDN for newborn

• Phototherapy- to break down bilirubin

• Hydroxycarbamide- to increase RBC production

• In severe cases- exchange transfusion (CMV negative)