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Rh isoimmunisation


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Rh isoimmunisation

  1. 1. Dr.Suresh Babu Chaduvula Professor Department of Obs & Gyn College of Medicine KKU, Abha, Saudi Arabia
  2. 2.  Karl Landsteiner – Proposed Blood Group Sysytem  Awarded Nobel prize in 1930  Landsteiner and S.Weiner – discovered Rhesus system in Rhesus monkeys.
  3. 3.  RBC cell surface has antigens called Agglutinogens or isoagglutinogens and plasma contains antibodies called Agglutinins or isoagglutinins.  A positive woman will have A antigen and anti B antibodies.  Rhesus positive mothers means D antigen positive.  Rhesus negative means D antigen negative mothers.
  4. 4.  There are 5 Rhesus antigens – D, C,c,E and e.  Out of which D antigen is most powerful antigen.  Other antigens like Kell and Duffy antigens.  Anti- kell is very serious.
  5. 5.  Sensitization of maternal immune system to produce antibodies after exposure to fetal RBC antigens.  Allo or Isoimmunisation – means immune response to foreign antigens from the same species.  Prevalence is 1%.
  6. 6.  1. Mismatched blood transfusion  2.Feto maternal hemorrhage following delivery, ectopic pregnancy, abortions.  3. Invasive procedures like Chorionic villous sampling, Amniocentesis in pregnant mothers  4. APH – Placenta Previa, Abruption of placenta  5. External cephalic version  6. Intrauterine fetal death
  7. 7.  Feto-maternal hemorrhage of Rh positive cells enter into maternal circulation and will produce anti – D antibodies Ig M type initially called – Sensitisation.  After a minimum period of 3 months IgG antibodies are produced which are capable of crossing placental barrier.  IgG antibodies attack and destroy fetal RBCs in spleen and produce Hemolytic anemia of Newborn.  Anemia will produce erythropoiesis in liver leading to erythroblast production called Erythroblastosis fetalis.
  8. 8.  In a mother who is already sensitised will have a very severe hemolytic anemia and hyperbilirubinemia called Icterus Gravis Neonatorum.  If this unconjugated bilirubin crosses blood brain barrier it will stain basal ganglia called Kernicterus  And hypo-proteinemia which will lead to changes in hemeodynamics results in accumulation of fluid all over the body and also in body cavities called Hydrops fetalis.
  9. 9.  Antenatally at 28 and 34 weeks Anti D Immunoglobulin of 300 micrograms should be given.[ decreases immunization by 0.2%]  Anti D Immunoglobulin of 300 micrograms should be given within 72 hours called RhoGAM.[ decreases immunization by 1.5%]  Following all invasive procedures also it should be given.  300 micrograms can protect from 30 ml of bleed.
  10. 10.  1. Increases with each subsequent pregnancy  2. Depends on paternal zygosity  3. Amount of feto-maternal bleeding  4.ABO incompatibility.
  11. 11.  Initially sensitization occurs in 1st pregnancy.  Later due to memory in the immune system response for antibodies will be very high.
  12. 12.  Amount of antibody production varies with the amount of fetal RBCs entered into maternal circulation.  Quantity tests for FMH is done by 1.Kleihuer-Betke test 2.Flow cytometry
  13. 13.  It occurs in mothers with ‘O’ blood group.  The antibodies in this group are weak hemolysins.  These can attach to only few fetal RBCs  It may produce only mild hyper bilirubinemia but not Hydrops.  These antibodies and mild hemolysis will decrease Rh iso- immunization and hemolysis.
  14. 14.  Do Blood group and type of partners  Anti D immunoglobulin at 28/ 34 weeks  Anti D immunoglobulin within 72 hours  Assess amount of feto-maternal hemorrhage and if amount is more than 30 ml adjust the dose.
  15. 15.  Assess accurately gestational age by USG  Blood group and typing of partners  Assess Antibody titer – by Indirect Coomb’s test – every 2-4 weeks  Amniocentesis – at a critical titer 1:16 to assess the hemolytic anemia
  16. 16.  To determine the amount of bilirubin which is produced by fetal hemolysis and is secreted by secretions from fetal body.  Spectrophotometric analysis is used to find out level of bilirubin in amniotic fluid.  Bilirubin causes shift of optical density from linearity. Shift is greatest at 450 nanometer.  Degree of shift at 450 nm called Delta OD [OD 450] indicates degree of hemolysis.
  17. 17.  Delta OD at 450 should be plotted in Liley chart.[used between 27 to 41 weeks]  I t has X axis –indicates gestation in weeks and Y axis about Delta OD.  It has 3 zones called Low, Mid and High Zone.  Delta OD may fall either of the zones and gives approximate time for time of delivery.  This chart also helpful in preventing iatrogenic preterm delivery.
  18. 18.  Low zone indicates - mild anemia -  Mid zone –mild to severe anemia  High zone – severe anemia and impending fetal death within 7-10 days.
  19. 19.  Like a normal pregnancy deliver at 38 weeks  Do regular ultrasound and may have to repeat amniocentesis.  Fetal well being tests – NST, CTG, Biophysical profile, Doppler study.
  20. 20.  High mid and High zone will require CORDOCENTESIS – to assess fetal hemoglobin, hematocrit , platelets and group and type, reticulocyte count fetal transfusion through umbilical vein and delivery. Transfusion of O negative fresh blood if hematocrit is less than 30%.
  21. 21.  1. Intra peritoneal  2. Intra vascular – umbilical vein  Transfusion can be given till fetal hematocrit becomes normal till the risk of prematurity is crossed.
  22. 22.  A] Ultrasound – to determine hydropic changes like 1. scalp edema 2. Anasarca 3. Effusions 4. Hepato and spleenomegaly 5. Umbilicalomegaly 6. Placentomegaly B] Doppler Velocimetry – Assess peak systolic velocity in middle cerebral artery, aorta, vena cava and umbilical vein. It will be increased in severe anemia. C] CTG – NST D] Biophysical profile
  23. 23.  Low Zone & Low Mid Zone - – Deliver at 38 weeks.  High mid zone High Zone – Deliver at 34 weeks electively by cesarean section .  Arrange adequate amount of O negative fresh blood for the newborn.  Inform the neonatologist prior to the delivery.  Higher tertiary centers is ideal place for delivery.