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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