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RH (Rhesus) Iso-immunzation
Blood group is defined in two ways.
1- The ABO group in which the person may have one of following group (A, B,
O, AB).
2- Rhesus system, which consist of C, D & E antigens(Ag).
The importance of these blood group systems is that:
A mismatch between the fetus and the mother can mean that when fetal RBC pass
across to the maternal circulation, as they do usually in pregnancy, sensitization of the
maternal immune system to the fetal ( foreign) red blood cell may occur.
ABO system immunization:
Can occur when the (mother is blood group O) and the (baby is blood group A
or B). Anti A & anti B are naturally present in the maternal circulation and not
required prior sensitization in order to be produced.
For that reason ABO incompatibility may occur in the first pregnancy, so anti- A or
anti – B antibodies (Ab) may pass to the fetal circulation causing fetal hemolysis and
anaemia.
ABO incompatibility cause usually mild hemolytic disease of the baby but may
sometimes explain unexpected jaundice in an otherwise healthy term infant.
Fortunately this disease is less severe than Rh incompatibility and few babies will
need treatment. 20% of the infant have ABO incompatibility but only 5% get overt
hemolytic disease.
Rhesus system isoimunization:
The rhesus system is more commonly associated with severe haemolytic disease;
the D type is that which associated most commonly with severe hemolytic fetal
disease.
Both Anti-C & anti- E antibodies may also associate with hemolytic disease requiring
intrauterine fetal blood transfusion, but are much less commonly associated with the
disease.
It’s an immunological process in which the RBC of the fetus and newborn are
hemolyzed by maternal isoantibodies (Abs capable of reacting with RBC from same
species but not with RBC of the individual producing the Abs) that have been able to
cross the placenta and affecting the fetus or the newborn. These antibodies are IgG
and IgM produces by the mother (IgG is the smallest molecule which can cross the
placenta) and it is the responsible one for fetal RBC destruction.
These antibodies formed in the maternal immune system (immunization) due to:
1- Fetal RBC bearing Ag foreign to the mother enter her circulation.
2- Follow incompatible blood transfusion.
Antibodies associated with hemolytic disease:
a. ABO
b. Rhesus (C, D, E)
c. Kell
d. Duffy
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e. c ( known as ‘little c’)
f. S
Prevalence of rhesus disease:
The prevalence of D rhesus negativity is 15 % in Caucasian population, but lower in
all other ethnic group. It is very uncommon in Orientals. In Iraq is around 5-6 %.
Rhesus disease is comments in countries where anti-D prophylaxis is not widespread,
such as Middle East and Russia.
Inheritance of the blood gp Ag are according to the Mendelian laws; Rh system
formed by six Rh gene carried on the short arm of chromosomes 1, three carried on
each chromosome, each tri gene inherited from each parents, 3 of the gene are
dominant (C, D, E) and 3 recessive (c, d, e), the most important is D gene which
determined the individual character of being Rh –ve or +ve and is the most important
to the obstetrician. D Ag responsible for 97% of the Rhesus disease while 1-2 % due
to C, E Ags or rarely due to other Ags.
Homozygous (DD) dominant transmission
Rh +ve person <
Heterozygous (Dd) recessive transmission
Rh –ve only homozygous (dd)
So homozygous Rh +ve father ( DD) if married to Rh –ve (dd) mother offspring
are Rh + ve 100%
If the father heterozygous (Dd) chance of the child Rh+ve 50%
So the problem arise only if a mother Rh –ve married to a father Rh +ve and
delivered a baby who is Rh +ve
Aetiology of Rhesus disease:
This disease does not affect the first pregnancy because transfer is minimum
before 12 weeks of gestation but increase slowly to the 24 weeks and then increase
until term, usually transfusion more during labour especially in the third stage of
labour so that Abs are uncommon to be formed in the first pregnancy.
If the mother exposed to D rhesus positive fetal cells in a previous pregnancy, she will
developed an immune response which show no effect until a following pregnancy
with a D rhesus-positive baby occur.
Feto maternal transfusion:
less than 0.1 ml of the fetal blood is sufficient to cause the initial sensitization
(primary response) to rhesus D antigen in the mother, that is occur few weeks after the
exposure to fetal blood, by IgM first then by IgG, but the maternal response varies
greatly and if the mother is sensitized she will show rapid increment in Abs titer
during subsequent pregnancy and the response will be magnify with successive
exposure if the fetus is also an Rh+ve and sensitization will never be lost.
Kleihauer test: is a test on maternal blood to determine the proportion of the fetal
cells present, use to demonstrate the presence of fetal cell in the maternal blood:
where a film of maternal blood is mixed with a weak acid solution then stained; fetal
RBC contain HbF (which is more resistant to denaturation with acid or alcohol than
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adult Hb) so fetal RBC can be counted which appear dark red and surrounded by
colorless ghosts which are adult Hb.
This will calculate the amount of extra anti-D immunoglobulin required should a large
transfusion have occurred.
Potential sensitizing events for rhesus disease:
1- Normal pregnancy: antenatal fetal transfusion. 5% occur in the first trimester,
40% in the 3
rd
trimester. Immunization in the normal pregnancy is 1-2 % of
pregnant Rh-ve female
2- Normal labour.
3- Miscarriage.
4- Termination of pregnancy.
5- Antepartum haemorrahage.
6- Invasive prenatal testing ( chorionic villus sampling, amniocentesis and
cordocentesis)
7- Failure of protection: when the dose of prophylactic Ig anti D is under
protective especially if she has macrotransfusion, so the dose of anti D should
be proportional to the volume of feto-maternal haemorrhage (FMT) which can
diagnosed by; kleihour test.
8- Obstetrical trauma increases the risk, if unprotected, eg. External cephalic
version (ECV), caesarean section and manual removal of placenta. In such
cases must give prophylactic anti D.
9- No protection: in pregnancy, labour, late ectopic or abortion (Especially in the
second trimester abortion) if blood group unknown or the patient in far
discrete area.
10- Mismatched blood transfusion: completely preventable.
Prevention:
300 microgram of anti- D can protect against 30 ml of blood or 15 ml RBC given IM
( its gama globulin – anti D Ig - ) prevent development of Abs by ( mop up) any
circulating rhesus positive cells before an immune response is excited in the mother.
Preferably within 72 hours of exposure to fetal red cells, but it can be given later even
up to 2 weeks but the protection will be less about 50%. Or it needs to be given as
soon as possible after any potential sensitizing events. The dose of anti-D depends on
the gestational age and the amount of FMH.
1-
In the first trimester of pregnancy
- because of volume of fetal blood is so small,
unlikely that sensitization would occur and the standard dose of anti-D is given
which will be more than enough to cover even the largest feto-maternal
transfusion at this gestational age.
2- In the second and third trimester-
fetal blood volume is more and possibility of
transfusion of several milliliters, a larger dose is given and kleihauer test
performed.
3- Prophylactic anti-D at 28 & 34 weeks:
is use routinely in some countries, depend
on the fact the small number of rhesus negative women become sensitized during
pregnancy despite the administration of anti-D at delivery and without a clinically
obvious clinical signs.
Other rhesus antigens (C & E) may also be associated with hemolytic disease of the
fetus or neonates, and are inherited in the same way as D.
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Diagnosis of immunization:
1- Maternal Antibodies.
a- Indirect coomb’s test: progressive double dilution of maternal serum
incubated with Rh+ve - O - RBC which cause agglutination.
b- Auto analyzer which give correct estimation by IU or micro gram/ ml
which is more quantitative and better if available
2- Amniotic fluid antibodies: if the level in AF 0.56 IU /ml and over mean she
carry affected fetus.
Pathophysiology
:
If the antibodies are present in sufficient quantities in the maternal circulation, it will
cross to the fetus during pregnancy and if he is Rh D- positive then hemolysis the fetal
RBC will occur and will be destroyed in the reticulo endothelial system.
Features of fetal anaemia are:
- Polyhydramios
- Enlarged fetal heart
- Ascites and pericardial effusions.
- Hyperdynamic fetal circulation (detected by Doppler ultrasound by measuring
increased velocities in the middle cerebral artery or aorta).
- Reduced fetal movement.
- Abnormal CTG with reduced variability then will have ‘sinusoidal’ trace.
In most severe cases
, the fetus become severely anemic with generalize oedema (
hydrops fetalis), has pleural and pericardial effusion with ascitis and eventually if
untreated can lead to IUD.
In less severe cases
the infant born alive with features of hemolysis (pallor, jaundice,
hepatosplenomegaly).
Note: Clinical and ultrasound feature of fetal anemia don’t usually became evident
unless fetal hemoglobin is <6 g/dl.
Cord blood at delivery guide the severity of the disease:
Sever if Hb < 10 g/dl
Moderate if 11-13 g/dl
Mild > 14 g/dl
After birth the level of jaundice may increase rapidly (before birth the excess
bilirubine is excreted into the maternal circulation by the placenta so that cord blood
at delivery for bilirubin is not reliable as an index of severity.
The spectrum of rhesus disease:
Mildest…..
- Normal delivery at term, mild jaundice may need phototherapy.
- Preterm delivery of an anemic fetus requiring exchange transfusion.
- Delivery of a fetus at 34 weeks following fortnightly blood transfusion from
26 weeks’ gestation.
- Still birth or neonatal death due to rhesus (earlier gestation=worse prognosis).
….(Severest).
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Management:
of RH – ve mother:
The most important preventive method is that we must know the blood group of the
female and her husband for every pregnant lady.
● Antenatal management:
1- History : blood group and RH of the husband, parity and past obstetrical
history to determined the severity of the problem and neonatal outcome and
management, previous babies blood groups and Rh and if received anti D or not
before.
2- Accurate determination of the gestational age.
Two groups of patient arise:
A-
Un immunized
follow up with Ab titer monthly from 20 weeks, and if
the titer remain negative so give prophylactic anti D: after any
obstetrical interference, at 28 weeks, and 34 weeks and after delivery
(if the newborn is Rh + ve, coomb’s test –ve for the mother and the
baby; for the baby is direct coomb’s test which detect fetal RBC
covered by antibodies.
And repeat the antibodies titer at 3-6 month after delivery.
B-
Immunized
female:
1-Antibodies titer:
Has rough correlation to the fetal outcome. Critical value depend on
the method usually 1/16 by indirect coomb’s and the most important is
increase titer of 2 tubes in same lab.
Usually it’s of value in the first affected pregnancy, do it every 4
weeks. And any increase in the antibody titer to > 15 IU/ml need fetal
assessment for anemia or may need invasive assessment.
2- Amniocentesis:
-- Indications: critical titer of antibodies, increase titer in
More than 2 tubes dilution, very bad obstetrical history.
--Timing of amniocentesis depend on the previous history,
that is 10 weeks before the earliest IUD, or birth of the
affected fetus. Usually at 28- 30 weeks, or when the level
of antibody titer is suddenly rise.
--Advantage; predict the severity, determine the time of
Intervention by newer technique or delivery and detect
the fetal lung maturity.
Always must be done under ultrasound guide to localize the site of placenta. And
repeat after 3-4 weeks.
Take 5-10 ml of AF required for spectrophotometric analysis, the sample kept in
brown bottle to prevent from exposure to sun light which give false low readings then
centrifuge, filtered and analyzed in spectrophotometric and the optic density reading
will show peack at 450 nm and the size of the peak is proportional to the amount of
pigment in the fluid. The result then plotted on Liley chart which is done in the third
trimester and according to it the degree of affection will be either very mildly affected
in Zone I, moderately affected in Zone II or severely affected in Zone III. Zone II is
divided into two part:
A- Above 50% is very serious so considered delivery or IUI
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B- Below 50% can wait and repeat
Complications:
1- Preterm labour
2- Bloody tap
3- Infection
4- Fetal anaemia
3- Biophysical surveillance:
A - U/S : used in case of amniocenteses or IU transfusion to locate the site
of placenta, can show signs of hydrops fetalis, but normal U/S not exclude
fetal affection.
So in sever fetal anaemia can see ascitis, hydrothorax, generalize odema,
oedema of the scalp, hepatosplenomegaly, pericardial effusion, dilated
umbilical vein,
Fetal maturity also can be shown by ultrasound.
B - Doppler U/S: increase blood velocity in the middle cerebral MCA
artery and aorta.
a- FHR by cardiotocography at each visit in the third trimester and
before and after amniocenteses, FBS or IUT.
4- Plasmapheresis: intensive plasma exchange in sever Rhesus disease,
relatively non hazards to the mother and the fetus and can improve
environment to the baby by decrease Ab titre.
Technique by removal of as much Abs as possible from maternal circulation,
done 3-4 X / week and remove 1-3 Lit of plasma on each occasion and can
decrease serum Abs level up to 75%.
5- Cordocentesis and intrauterine transfusion (IUT):
Cordocentesis is the only reliable method to determine the severity of the
disease in the second trimester, it measure the fetal haemoglobin, PCV, Retic
count, blood group and Rh (since if the fetus is Rh negative then there will be
no need for further management and he will not develop rhesus disease) ,
with direct coomb’s test. Done under U/S guide and take the sample from
umbilical vein and determined the need for IUT.
IUT either intraperitoneal or intravenous. Usually done between 25 and 32
weeks. Using packed cell O –ve blood compatible with maternal blood, its (
Hb between 22-24 g/dl.), cytomegalovirus negative and irradiated (to
decrease the risk of graft-versus-host disease).
Side effect of intrauterine transfusion:
1. Operative mortality, fetal risk 10-20%.
2. Antibodies boosted
3. Preterm labour or premature of memebrane
4. Fetal thrombocytopenia
5. Fetal bradycardia
6. Technical difficulties
7. Unexpected fetal death
6- Combined methods:
Ex, plasmapheresis + IUT to decrease the number of transfusion.
7- Preterm labour or neonatal intensive care management
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8- Delivery: the fetus must be delivered in the best possible condition apart from
hemolytic disease, need continuous intrapartum monitoring, low threshold for
caesarean section
●Post natal management:
- The use of prophylaxis Anti-D, and counseling about contraception
- Neonatal: (blood must always be available before the delivery, if the fetus
suspected that will need exchange transfusion).
Cord blood sample: for CBP, blood group and Rh. Direct coomb’s test,
bilirubin level (direct and indirect).
Management immediately after labour depend on Hb level if low so exchange
transfusion, but subsequent management depend on bilirubin level.
Phototherapy and phenobarbitone can be of help.
Factors which influence the incidence of the disease are:
1- The dose of blood which enter the maternal circulation.
2- Coexistence of ABO incompatibility between the mother and the fetus.if the
mother group O and father A, B, or AB so the frequency of sensitization is
decrease.
3- 30-35% of Rh-ve mother are (non responders) can’t be immunized.
4- Prophylaxsis: in countries of high stander of health its practice to give every
Rh-ve female an anti –D injection after every trauma, manipulation or
delivery.
5- Repetition of pregnancy: with each time IgG form more rapidly and the
condition is progressive.
6- Primigravida.
Prognosis:
It is a progressive disease, prognosis depend on the:
Titer at early pregnancy, genotype of the male, if can get the blood group of the baby
and available method for treatment.
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Question to be answered:
A 32-year-old woman, P1101, and her new husband present for prenatal
care at 20 weeks’ gestation. Her past obstetric history is significant for a
first child delivered at term following an abruption. Her second child died
of complications of prematurity following in utero transfusions for Rh
isoimmunization. Her initial prenatal labs this pregnancy indicate her
blood type as A negative and an antibody screen positive for anti-D with
a titer of 1:64.
Q: You discuss any additional evaluation needed, her risks in this
pregnancy, and the plan of management with her and her husband.
Note:
P1101: 1 one term
1 preterm
0 Abortion
1 living