RH ISOIMMUNISATI

ONDr.Suresh Babu Chaduvula

ProfessorDepartment of Obs & Gyn

College of MedicineKKU, Abha, Saudi Arabia

INTRODUCTION

Karl Landsteiner – Proposed Blood Group Sysytem

Awarded Nobel prize in 1930 Landsteiner and S.Weiner – discovered

Rhesus system in Rhesus monkeys.

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.

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.

RH ISO OR ALLO IMMUNISATION 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%.

CAUSES OF RHESUS ISOIMMUNISATION 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

PATHOPHYSIOLOGY 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.

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.

PREVENTION OF ISO-IMMUNISATION 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.

SEVERITY OF DISEASE VARIES: 1. Increases with each subsequent

pregnancy 2. Depends on paternal zygosity 3. Amount of feto-maternal bleeding 4.ABO incompatibility.

SUBSEQUENT PREGNANCY Initially sensitization occurs in 1st

pregnancy. Later due to memory in the immune

system response for antibodies will be very high.

FETO MATERNAL HEMORRHAGE 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

ABO INCOMPATABILITY 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.

MANAGEMENT – RH NEGATIVE WOMEN WHO ARE UNSENSITIZED 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.

MANAGEMENT – RH NEGATIVE WOMEN WHO ARE SENSITIZED 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

AMNIOCENTESIS 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.

LILEY’S CHART 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.

Low zone indicates - mild anemia -

Mid zone –mild to severe anemia

High zone – severe anemia and impending fetal death within 7-10 days.

LOW ZONE 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.

MID AND HIGH ZONE 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%.

TRANSFUSION 1. Intra peritoneal

2. Intra vascular – umbilical vein

Transfusion can be given till fetal hematocrit becomes normal till the risk of prematurity is crossed.

NON INVASIVE TESTS 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 – NSTD] Biophysical profile

DELIVERY 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.

THANK YOU ALL AND ALL THE BEST