ISOIMMUNISATIONWilliam 2001

I. Fetal anemia II. Fetomaternal hemorrhageIII. IsoimmunisationIV. Immune hydropsV. ManagementVI. PerventionVII. Large fetomaternal Hge

FETAL ANEMIA

Normal fetal Hb% > 35 weeks = 17 gm/dLFetal anemia = < 14 gm/dLCauses:

Placenta cut or torn Fetal vessel perforation Raising the neonate above the abdomen of his mother before clamping the cordDelayed clamping of the cord ↑ offetal Hb by 20%

FETAL-TO-MATERNAL HEMORRHAGE

Common in all pregnanciesRarely > 30mL = 0.3 – 0.6%Benefit in fetal karyotypingKeihauer – Batke test:

Identify fetal RBCs by acid elusion darker than maternal RBCs

Rosette test:Maternal blood + anti D Ab+ indicator

fetal blood surrounded by AbsMore accurate in hemoglobinopathy

Severe anemia sinusoidal FHR not pathognomonic evaluate immediately

Chronic anemia may normal FHRSignificant acute /chronic Hge may Neurological impairment due to:

Hypotension ↓ perfusion Ischemia CNS infarction

Obstetric management may not improve CNS damage

Large fetal Hg may fetal deathin 5% and the cause may be unknown

e.g. chorioangiomaPlacental abruption:

usually mild Hg except if traumatic

Quantification of volume of blood loss:

influence management Determine the dose of Anti D Ig

Fetal red cells =maternal Hct X maternal blood volume X % of fetal cells in Kleihauer

- Batke test ÷ neonatal Hct Causes of fetal-to-maternal Hg:

Early abortion Elective abortion

Ectopic Amniocentesis Cordocentesis Chorionic villous sampling Antepartum trauma Placental abruption Fetal demise Manual placental extraction External version

ISOIMMUNISATION

ABO blood group CDE blood group Other blood groups Kell antigen Other antigens

History:1892 Ballantin hydrops fetalis1932 Anemia and reticulosis are

present in hydrops fetalis1940 Landsteiner & Weiner

Rh factor1941 Levein hydrops is caused by maternal isoimmunisation

by Rh –ve fetus1961 Anti Rh

-Fetal blood contain > 400 Ags most of them are insignificant

-Most people inherit at least 1 Ag from their fathers that is lacking

in their mothers -Isoimmunisation of an Rh –ve

pregnant woman occur as a result of :

Rh +ve fetus Blood transfusion

Isoimmunization is rare because:

Variable Ag amounts Variable antigenicity Maternal immune respond ↓ placental passage ABO incompitability destruction of fetal RBCs

Not all isoimmunization hydrops2% of all women are isoimmunized

6 months postpartum %of isoimmunisation with Rh-ve

ABO compatible fetus: 2% at delivery

7% 6 months postpartum 7% next pregnancy

Total = 16%

ABO blood group incompatibility: -The most common cause of hemolytic

disease of the neonate -20% of all fetuses are ABO incompatible

only 5% of them are clinically affected - Mild anemia & ↑ reticulocytes

-No erythtoplastosis -Treated by phototherapy

Difference from Rh incompatibility: Affect 1st baby Milder ( Ig M does not pass placenta) Rarely progressive Affect African Americans

Criteria of ABO incompatibility: 1st day jaundice Mother O, fetus A,B,or AB group Anemia, ↑ reticulocytes

Management of ABO incompatibility:Same as Rh isoimmunization but:

No amniocentasis No blood transfusion

Because there is no hydropsCDE blood group:

5 types: c, C, e, E, D

-D is +ve if present and –ve if absent -D isoimmunisation is the most common

isoimmunization -D –ve pregnant women are sensitized if

their fetus is D +ve -CDE genes are inherited independent on

other blood groups -They are located on chromosome 1

Geographic distribution of D +ve populations:

Native Americans and Chinese 95% African Americans 92% Caucasians 87% Basque 76%

Other blood groups: % = 1 -¼ Lewis blood group mild

jaundice starts weeks postpartum -74% D, C, c, E & e antigens

-Recently Rh isoimmunization is ↓ due to Anit D treatment

-Now Rh = 40% Other Ags = 60%

Kell antigen: -Caucasian kell +ve = 91%

-Isoimmunisation occur by pregnancy or blood transfusion

- Much earlier and more severe anemia which can not be predicted

by: Maternal titer AF bilirubin = mild/moderate

-May fetal death inspite of:Blood transfusionNormal AF bilirubin

-Hemolysis ↓ due to: ↓RBCs

↓bilirubin -If maternal anti-Kell Ab titer ≥ 1 : 8

Cordiocentesis because AF bilirubin is out of proportion to anemia

Other antigens:Kid Ag:

Jk a –ve = 25% Jk b –ve = 25% Jk a - b +ve = 50%

Duffy Ag:Fy a – b –ve in some blacksC Ag :

Most common Ag after D Moderate to severe hemolysis

IMMUNE HYDROPS

Immune hydrops Hyperbilirubinemia Mortality Identification of isoimmunization Fetal Rh genotype

IMMUNE HYDROPS

RBCs hemolysis by isoimmunization Hyperplasia of BM Hyperplasia of extramedulary

sites: Liver Spleen

Liver:Fatty degenerationDeposition of hemosidrineLarge canaliculi with bile

Heart: HFLungs: Hge - immatureWhen fluid accumulate in subcutanoustissues hydrops fetalisDefinition:Abnormal fluid in ≥ 2 sites:

Ascitis – oedema – pleural effusion

Placenta: Enlarged cotyledons Odemotus villi Boggy

Fetus: Dystocia due to: Hepatospleenomegaly Odema

PATHOPHYSIOLOGY

Heart:HF hypoxia capillary leakageExtramedulary hyperpleasia:

Hepatic parynchemal distruction portal HTN umbilical vein HTNLiver disease : ↓ protein ↓ colloidal osmotic P

Study: Cordiocentesis in hydrops:

Hb = < 3.5 gm/dL Plasma protein = < 2 SD AF plasma protein ↑

The degree of anemia affectthe degree of ascitis and madeworse by ↓ plasma proteins

Capillary endothelial damage : Capillary leakage ↓ proteinStudy:

↑Umbilical vein pressure is due tocardiac dysfunction and notportal HTNSinusoidal FHR = impending death

Neonate: Pale Edematous Limp ↑ need for resuscitation Dyspnea Collapse Hepatospleenomegaly Petechiae ecchymosis

HYPERBILIRUBINEMIA

Less affected fetuses are born normal jaundice within hoursIf untreated kernicterus = CNS damage affecting basal gangliaMortality:Reduced dramatically due to:

D Ig Blood transfusion Induction of labor

IDENTIFICATION OF ISOIMMUNIZATION

Maternal serum Abs : Unbound to RBCs disappear

within 1 – 4 months Indirect Coombs T

Fetal serum Abs : Bound to RBCs hemolysis

Direct Coombs testNeonatal blood group:

Inaccurate because D-Ag may be coated with D-Ab

If maternal Abs are present : Ig G or Ig M ?

(Ig M can not pass the placenta)If Ig G antibody titer:

< critical value 1 : 16 repeat > critical value 1 : 16 evaluate

Critical values for other Ags: Kell ≥ 1 : 8

C, E ≥ 1 : 32

The presence of Abs in the mother does not mean that:

The fetus is +ve He will be affected

Amnestic response: = ↑Ab titer + Rh –ve fetus

Because ½ of adult males are heterozygous for D Ag

¼of women at risk are Rh -ve

Estimation of fetal genotype:The father is tested for:

Blood group Most likely arrangement of his CDE

genes = presumed genotype based on the most common arrangement

of genes in men of his raceIf the father is white:

94% chance to be heterozygous 47% chance of having D –ve fetus

MANAGEMENT

Amniotic fluid evaluation Expanded Liley graph Fetal blood sampling Subsequent child development Other methods to ↓ hemolysis Delivery Exchange transfusion Prevention Routine antepartum anti-D

AMNIOTIC FLUID EVALUATION

↑Hemolysis ↑ AF bilirubin

↑ anemia

Since AF bilirubin is very small

measured by a continuously recording spectrophotometer and is demonstrable

as a change in absorbance at 450 nm

(∆OD 450 ) then the results are

plotted on Liley graph (1961)

LILEY GRAPH

Zones of Liley graph:Zone 1 = mild anemia

= 14 gm% Zone 2 = moderate/severe anemia

= 13.9 – 8 gm% Zone 3 = severe anemia

< = 8 gm% = death in 7 – 10 days

If the results are in zone 1 or 2 :repeat in 1 – 2 weeks and draw a line between the 2 results:

-If the trend of the line is: Decreasing Parallel to the lines of the graph

= unaffected fetus or stable repeat / 2 – 3 weeks until

transfusion or delivery

-If the trend of the line is: - Rising within the zone

- Rising to zone 3 = Unstable

Managed as zone 3If the results are in zone 3:

= Severe anemia Immediate blood

transfusion or delivery

Expanded Liley graph:Since Liley graph was made for fetuses

>27 week, expanded graph back to18 – 20 weeks is inaccurate, because

AF bilirubin < 25 weeks is highSo, in cases of:

Hydrops < 25 weeks Severe anemia < 25 weeks

It’s better to do cordocentesis

FETAL BLOOD SAMPLING

Cordocentesis is risky # amniocentesisAdvantages: blood typingRecently amniocytes for Rh typing:

100% accurate 99.7% sensitivity 94% specificity Also for C,E , Kell & other Ags

If fetus is Rh–ve no further testsIf amniocentesis possible anemia U/S hepatomegaly NST/BPP fetal stress immediate blood transfusion or delivery

Tests of cordocentesis: Hb% HTV Indirect Coombs titer Reticulocyte count

Indications of IU blood transfusion: Hb 2 gm/dL < mean of normal Hb in the fetuses in the same GA HTV 30% = 2 SD < mean at all GAs

Methods of intrauterine blood transfusion:

Intraperitoneal - intraumbilicalSubsequent child development:

90% normal – delayed - abnormal Other methods to ↓ hemolysis:

Plasmapheresis Large dose of promethazine Corticosteroids for immunosuppresion D +ve erythrocyte membrane capsulesAll are ineffective

DELIVERY

Aim: =Delivery at or near term

Monitor by fetal wellbeing tests If the fetus is very immature: Intrauterine blood transfusion

If near term: deliver If lungs are mature induce labor If compromised fetus CS

EXCHANGE TRANSFUSION IN THE NEWBORN

If the mother is sensitized cord blood sample for:

Hb% Direct Coombs test

If overtly anemic exchange blood transfusion by O –ve fresh blood

If not overtly anemic the need for blood transfusion is determined by:

The rate of bilirubin ↑ Maturity Complications

PREVENTION

By anti D Ig = 7S Ig G = 300 μg D AbGiven within 72 hours of deliveryTo none sensitized mothers onlyGiven after: abortion, mole, ectopic,

miscarrageRate of sensitization without D Ig:

2% of spontaneous abortion 5% of elective abortion 6% of amniocentesis

ROUTINE ANTEPARTUM ADMINISTRATIONAt 28 weeks For all Rh –ve pregnant women

↓isoimmunization from 1.8 % to 0.07%In the past:

2nd injection 34 weeks ½life of Ig:

=24 hours Reduce titer by time weak +ve indirect Coombs test

Now the 2nd injection is given if: Fetomaternal Hg occurs Amniocentesis > 3 weeks from the 1st injection

The 2nd dose is against: 15 mL of D +ve RBCs 30 mL of fetal blood

Sometimes Ab cross the placenta Weakly +ve direct Coombs testRecognized by:

No anemia No hyperbilirubinemia

Risk of transmission of diseases: HIV inactivated by the factory hepatitis patients are excluded from donation very low risk

LARGE FETAL–TO - MATERNAL HG

Rarely 1 dose of Anti D Ig is insufficient =Very rare occur 1 : 1250 deliveries

To avoid this all Rh –ve women shouldbe tested after delivery by Kleihaure-

Batke or rosette testsNumber of ampoules :

= fetal blood/15

Du antigen:A variant of D antigen :

Du +ve & Du -veLess antigenic Treated as Rh D –veMaternal to fetal Hg:Very rarely an Rh –ve female fetus is sensitized inutero by her mother

=Grandmother theoryNo need for Anti D prophylaxis