Fetal Haemolytic Disease

1. Fetal Haemolytic Disease

2. Maternal antibodies develop against fetal red blood cells IgG antibodies cross the placenta Haemolysis, anaemia, high-output cardiac failure & death

3. Usually a problem with subsequent pregnancies but may occur in the index pregnancy

4. Causes • ABO – does not usually cause significant haemolytic disease. • Anti-Kell – causes fetal bone marrow aplasia. • Rhesus – D antigen anti-D c antigen anti-c E antigen anti-E

5. Incidence • Approx 17% of the population is Rh-ve 10% of women at risk of developing anti-D. Incidence 1/1000 pregnancies

6. Predisposing Factors • Miscarriage and ectopic pregnancy • Invasive procedures • ECV • Abdominal trauma • Antepartum haemorrhage • Labour and birth

7. Initial exposure Small IgM response Subsequent exposure Large IgG response

8. IgG crosses placenta Forms antigen-antibody complex on red cell Red cells phagocytosed Anaemia and haemolysis

9. Anaemia • Fetal hypoxia • Hepatic and cardiac dysfunction • Oedema, ascites, pericardial & pleural effusions - HYDROPS

10. Haemolysis • Increased bilirubin • Jaundice postnatally • Kernicterus

11. Prevention • Anti-D after any sensitizing episode after 12 weeks • Consider routine prophylaxis

12. Management • Check antibodies at booking and 3rd trimester • If antibodies present – check antibody levels every 4 weeks to 28 weeks and then 2-weekly to term • <4IU/ml – severe disease rare • 4-15IU/ml – moderate risk • >15IU/ml – 50% risk of severe anaemia

13. Check paternal genotype D antigen autosomal dominant Father DD – fetus Rh positive Father d/D – 50% chance that fetus will be Rh+ve

14. Measurement of blood velocity in middle cerebral artery. • Hyperkinetic circulation correlates with fetal anaemia and need for further treatment.

15. Anti-D for sensitising events after 12 weeks. • If anti-D antibodies present do not give more anti-D. • Serial measurements of Anti-D levels. • Observe for signs of fetalanemia – if anemic transfuse or deliver.