SALSO Series - Rhesus Isoimmunisation

1. Rhesus isoimmunization

3. ABO blood group No No Yes Yes AB Yes Yes No No O No Yes Yes No B Yes No No Yes A Anti-B Anti-A Antigen B Antigen A ABO blood type

4. Rhesus blood group No No Rhesus –ve No Yes Rhesus +ve D-antibody D-Antigen D D D D D D D D D D D D D D D D

5. Epidemiology <1% Asians 5-10% African-Americans (Blacks) 15% Caucasian Racial variation in incidence of Rh negative

7. Basic - Isoimmunization Fetomaternal haemorrhage – fetal RBC enter maternal circulation Formation of antibodies to D antigen (anti-D) - sensitization Later in pregnancy or next pregnancy, anti-D crosses placenta Anti-D attacks fetal Rh +ve RBCs and are destroyed by the immune system – haemolytic anaemia

12. Risk of isoimmunisation 0.1-0.2% Postpartum + antepartum RhoGAM 1-2% Postpartum RhoGAM 8% Subsequent pregnancy - untreated 16% 1 st Rh-incompatible pregnancy – untreated Risk of isoimmunisation

21. Oxford Rhesus Therapy Unit mx guidelines 34+ Yes 2 > 16.0 34-38 Yes 2 10.1-16.0 36-38 No 2 4.1-10.0 Term No 2 0.5 - 4.0 Term No 4 < 0.5 Gestation at which delivery advised Invasive testing Repeat antibody quantitation (weeks) Anti-D quantitation (IU/ml)

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