Rhesus Isoimmunisation

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SALSO Series - Rhesus Isoimmunisation

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Rhesus Isoimmunisation

  1. 1. Rhesus isoimmunization
  2. 2. Basic – Blood group & Rhesus <ul><li>2 most important blood group systems </li></ul><ul><ul><li>ABO group </li></ul></ul><ul><ul><li>Rhesus group </li></ul></ul>
  3. 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. 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. 5. Epidemiology <1% Asians 5-10% African-Americans (Blacks) 15% Caucasian Racial variation in incidence of Rh negative
  6. 6. Basic - isoimmunization <ul><li>Occurs when: </li></ul><ul><ul><li>Mother is Rh –ve </li></ul></ul><ul><ul><li>Baby is Rh +ve </li></ul></ul><ul><ul><li>Fetomaternal haemorrhage occurs </li></ul></ul><ul><ul><ul><li>Antepartum haemorrhage </li></ul></ul></ul><ul><ul><ul><li>Falls or closed abdominal trauma </li></ul></ul></ul><ul><ul><ul><li>Intrauterine death </li></ul></ul></ul><ul><ul><ul><li>External cephalic version </li></ul></ul></ul><ul><ul><ul><li>Invasive prenatal diagnosis (e.g. amniocentesis, chorionic villus sampling) </li></ul></ul></ul>
  7. 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
  8. 8. Importance <ul><li>Rh –ve mothers are at risk of developing Rh isoimmunization if the fetus is Rh +ve </li></ul><ul><li>If a mother has been sensitized before, there is a risk of the Rhesus +ve fetus developing hemolytic anaemia and in severe cases, hydrops fetalis </li></ul>
  9. 9. How to prevent isoimmunization? <ul><li>Prevent mother from forming Anti-D antibodies by giving RhoGAM (Anti-D antibodies) </li></ul>
  10. 10. Why RhoGAM? <ul><li>Prophylactic anti-D Ig has resulted in a substantial fall in perinatal mortality and morbidity from rhesus D disease </li></ul>
  11. 11. Rhesus +ve men <ul><li>55% are heterozygous (Dd) – 50% chance of Rh-positive fetus </li></ul><ul><li>45% are homozygous (DD) – 100% chance of Rh-positive fetus </li></ul>
  12. 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
  13. 13. Indications for RhoGAM <ul><li>Miscarriage </li></ul><ul><ul><li>All therapeutic termination – irregardless of gestational age or methods (medical or surgical) </li></ul></ul><ul><ul><li>All surgical evacuation (ERPOC @ S&C) </li></ul></ul><ul><ul><li>Threatened miscarriage >12 weeks </li></ul></ul><ul><ul><li>Threatened miscarriage <12 weeks with </li></ul></ul><ul><ul><ul><li>Heavy or repeated bleeding </li></ul></ul></ul><ul><ul><ul><li>Abdominal pain </li></ul></ul></ul>
  14. 14. Indications for RhoGAM <ul><li>Ectopic pregnancy </li></ul><ul><li>Conditions a/w fetomaternal haemorrhage </li></ul><ul><ul><li>Antepartum haemorrhage </li></ul></ul><ul><ul><li>Falls or closed abdominal trauma </li></ul></ul><ul><ul><li>Intrauterine death </li></ul></ul><ul><ul><li>External cephalic version </li></ul></ul><ul><ul><li>Invasive prenatal diagnosis (e.g. amniocentesis, chorionic villus sampling) </li></ul></ul>
  15. 15. Not indicated <ul><li>Complete spontaneous miscarriage <12 weeks </li></ul><ul><li>Threatened miscarriage <12 weeks POA (with cessation of bleeding before 12 weeks POA) </li></ul><ul><li>Reason – unlikely to cause significant FMH </li></ul>
  16. 16. RhoGAM – Dosage & administration <ul><li>Dose </li></ul><ul><ul><li>Before 20 weeks : 250 IU </li></ul></ul><ul><ul><li>After 20 weeks : 500 IU </li></ul></ul><ul><ul><li>Postpartum : At least 500 IU </li></ul></ul><ul><ul><li>Note : Kleihauer test should be performed when anti-D Ig is given after 20 weeks </li></ul></ul><ul><ul><ul><li>To estimate volume of FMH </li></ul></ul></ul><ul><ul><ul><li>Additional anti-D Ig if FMH > 4 mL fetal cells (125 IU prevents immunization with 1 ml fetal cells) </li></ul></ul></ul>
  17. 17. RhoGAM – Dosage & administration <ul><li>Route : Deep IM injection – preferably deltoid muscle </li></ul><ul><li>Timing : Postpartum – <72 hours </li></ul><ul><ul><li>May still be given if presented later (10-14 days) </li></ul></ul>
  18. 18. Clinical setting <ul><li>Refer to hospital as early as possible if: </li></ul><ul><ul><li>Rhesus negative pregnant mother (either 1 st time detected or known rh –ve previously) </li></ul></ul><ul><ul><li>Known rhesus negative with risk of FMH (e.g. threatened miscarriage, APH, fall, abdominal trauma, etc.) </li></ul></ul>
  19. 19. Clinical setting <ul><li>Screened for maternal anti-D (sensitization) – Indirect Coomb’s test </li></ul><ul><ul><li>At booking </li></ul></ul><ul><ul><li>Just before 28 weeks </li></ul></ul><ul><li>If not sensitized, RhoGAM is administered: </li></ul><ul><ul><li>500 IU at 28 & 34 weeks </li></ul></ul><ul><ul><li>1,500 IU at 28 weeks only </li></ul></ul><ul><ul><li>No need to check Indirect Coomb’s test after Rhogam as it may be positive due to Rhogam itself </li></ul></ul><ul><ul><li>Postnatal RhoGAM is still given </li></ul></ul>
  20. 20. Clinical setting <ul><li>If sensitized, close monitoring of: </li></ul><ul><ul><li>Fetus </li></ul></ul><ul><ul><li>Anti-D level </li></ul></ul><ul><ul><li>Timing and mode of delivery depending of status of fetus </li></ul></ul>
  21. 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)
  22. 22. Non-invasive fetal monitoring <ul><li>Ultrasound – features of hydrops </li></ul><ul><ul><li>Ascites </li></ul></ul><ul><ul><li>Pleural effusion </li></ul></ul><ul><ul><li>Soft tissue/scalp edema </li></ul></ul><ul><ul><li>Cardiomegaly </li></ul></ul><ul><ul><li>Hepatomegaly </li></ul></ul><ul><li>Doppler – middle cerebral artery </li></ul><ul><li>FKC </li></ul><ul><li>CTG </li></ul>
  23. 23. Thank you

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