Rh allo-immunisation

Dr.Sareena GilvazProf & HOD of OBGJMMCH, Thrissur

Rhesus Blood group System

• Five red cell antigens C, c, D,E and e• Rh negative is absence of D antigen

• C, c, E & e antigens can cause erythroblastosis fetalis

• Lower immunogenicity than D• No severe disease • Hence not routinely tested

• Kell sensitization can be more severe than D

• But fewer erythro. are produced less haemolysis

• Anaemia from Kell sensitization > severe than indi. by AF bilirubin

• cut off for anti kell titre is 1:8 or greater

ABO group system• Most common cause of haemolytic dis • Anti A & anti B (IgM) cannot reach fetal

erythrocyles• Resulting anaemia usually mild• Freq seen in first born infants. • Can affect future preg’s but not progressive• No erythroblastosis fetalis • Most often only phototherapy required

Pathophysiology in Rh - D

• D immunisation excessive & prolonged anaemia

• Marked marrow erythroid hyperplasia• Extra medullary erythropoiesis spleen & liver

Hydrops pathophysiology

1.Heart failure from profound anaemia2.Hepatic dysfunction &

hypoproteinaemia

colloid on.pr. ascites etc

3.Tissue hypoxia cap. Endo. leak – hydrops

Immune hydrops

Hb <5gm % in hydropsAb. collection of fluid in 2 or more area of fetal body cavities Eg skin, ascites, pl.eff pericardial eff.

Hydropic placental changes placento megaly, can cause PE. Pre eclampsia in mother severe odema in mother mimicking fetal odema

-mirror syndrome

• Formerly called iso immunisation • Now called allo immunisation • Neonatal complication called

haemolytic disease of newborn HDN

Fetal genotyping performed on :

a. Ch. villous amniocytesb. Fetal bloodc. Non invasive fetal D genotype using cell

free fetal DNA in mat plasma (used in UK) 85-95% accuracy cell free fetal DNA

Identification of allo -immunised preg

• Routine practice to perform antibody screen at prenatal visit & unbound antibody in mat serum detected by indirect coombs test.

ICT

• Patient serum incubated with Rh +ve RBCs

• Washed 3 times to remove non adherent proteins

• Then suspend in anti-human glob. (Coomb’s serum)

• Expressed as highest dilution of serum causing agg.

Sensibilization

• In sensiblized women anti D antibodies are low .

• Not detected during this index preg. • Instead indentified early in a subsequent

preg when rechallenged by another D positive fetus

• Previously sensitized preg • Antibody titres high in subsequent

preg • But fetus D negative - amnestic

response

Sensitized pregnancy

• ICT +ve - critical value 1:16• Safe level of anti D antibody level is <15

IU /ml• Fetal / neonatal disease

A.F bilirubin Measured by a spectrophotometerChange in absorbance at 450mmThis diff. referred to as OD450

• Plotted on a graph div. Into three zones of Liley

• Liley’s graph 27- 40 wks & 3 zones• Zone I = D neg fetus or mild anemia• Zone II = lower zone 2 Hb 11-13.9g%

Upper zone 2 Hb 8 – 10.9g% -(premature delivery or IUT)

• Zone III indicates severe anemia Hb <8g%(Fetal death likely in a wk )

• Liley’s graph subsequently modified by Queenan

• Between 14-40wks • Large indeterminate zone where bilirubin

conc.does not predict fetal Hb conc.

• In many centres PSV in MCA has replaced amninocentesis for fetal anemia

• As anemic fetus preferentially shunts blood to brain to maintain adequate oxygenation

Diag techniques 1.Amniotic fluid bilirubin conc2.Serial USG doppler –fetal MCA –PSV3.USG for fetal assessment4.Fetal blood sampling

MCA-PSV• Accurate non invasive method for the

diagnosis fetal anemia ( Mari et al 1995)• 18-35wks• Before 18wks difficult & after 35wks

false +ve

Threshold of >1.5 MOM identified for fetuses with severe anemia (sensitivity 100%)

• If PCV >1.5MoM ,then fetal blood sampling reqd. for determining need for transfusion

• When haematocrit below 30% give intrauterine transfusion

Fetal blood transfusion

• When haematocrit below 30% • 2 std deviations below mean at all

gest. ages

Indication for FBS (1-2 % fetal loss)

(Cordocentesis )

• Zone II & III on Liley’s curve• PSV >1.5MoM• Hydrops on USG

USG

USG to detect the progress of dis. from mild to severe

1.Hepatosplenomegaly2.in portal venous diameter flow velocity

(N<5mm)3.Fluid in serous cavities ( pericardial effusion first)4.Subcutaneous odema – later 5.Liquor disturbances –poly hydraminos 6.Placentomegaly

Routes of intrauterine transfusion

Intraperitoneal IntravascularIntracardiac

Umb.vein Intra hepatic portion of

umb.vein

• With early onset haemolytic disease intra peritoneal transfusion done as vascular access difficult in the cord

• For intraperitoneal transfusion Gest .age – 20 x 10 =-ml

Nicholaides Chart• Mean fetoplacental bl. Volume (left e.g 100ml at 27 weeks)

• Multiplied by F ( right e.g 0.8 for a pre transfusion fetal hct of 10%.

And a donor hct of 80%)

Accurate method to give exact amount blood can be calculated usingMean Feto pl.bld.vol. x F = vol transfused

• O-ve double packed RBC with haematocrit 75-85%

• It should be screened • Aim is to increase fetal Hct to 50% with

the IUT

Timing of delivery

• Depends upon the severity of disease & neonatal facilities

• Steroids for lung maturity• Deliver by 37-38wks (never beyond

40wks)

Management during labour

• Cont.CTG monitoring(sinusoidal pattern late decel)

• Early cord clamping• Avoid methergine• No MROP• Cord kept long• Take cord bl. for Hb, Hct, DCT, Bld Gp &

Rh

Anti D immunoglobulin

• Std dose 300g of anti D in non sensitised mother

• ACOG 50 g mini dose for early preg. indication

Note

• Anti D not required in spont.abortion less than 12wks with out surgical intervention

• If in doubt give anti D• In vesicular mole now thought that

trophoblast cells may express D antigen. Therefore give Anti D

300 g is for 15ml fetal haematocrit

or

30 ml or of fetal blood

Kleihauer Betke test• Proformed on mat.bld to assess feto

mat.bleed• To mat.bld add acid solution ( citric acid

PO4 buffer)• Acid will elute adult Hb – ghost cells .• Fetal cells look dark red

• 80 fetal red cells in 50 low power field =4ml of

feto maternal hge

100 g of anti D will neutralize 4ml of feto mat. hge

Routine antepartum administration

• Prophylactically to all D –ve women at 28 wk(300 g)

• Second dose after deli if infant +ve • Without prophylaxis 1.8% woman sensitised with prophylaxis only 0.07%

(IInd dose routine as half life of immunoglobulin is 24days

protective levels predictably persist for 6wks or so)

• ed risk large feto mat.Hge 1. Abd trauma 2. Pl.abrutpito 3. Pl.praevia 4. Intrauterine

manipulation 5. Multifetal gest

6. MRP

Kernicterus

• Unconjugated hyper bilirubinaemia in the newborn

• Unconjugated bilirubin deposition in basal ganglia & hippocampus

• Profound neuronal degeneration • Surviving infants show -spasticity

muscular incoordination M.R

Positive correlation bet bilirubin levels >18-20 mg% & kernicterus

• Phototherapy –light increases oxidation of bilirubin .Thus enhances renal clearance & lowers s.bilirubin

Other treatment modalities

• Plasma pheresis• IV Immunoglobulin therapy• D positive erythrocyte mems in enteric

capsules• Immunosuppression with corticosteriods • Administration of promethazine

None have proved beneficial

In repeated preg loss

• IVF with embryo biopsy & transfer only if Rh-ve embryos

• Donor insemination from Rh –ve male donor