Rh Isoimmunization

Rh positive fetus

E, c, e.
A person who lacks D antigen is called

Rh negative.
15% of Caucasians, 5% African Americans and 2 % of Asians are Rh negative.
Rh isoimmunisation is due to D antigen in more than 90% of cases.
Occasionally hemolytic disease of the newborn is a result of maternal immunization to Irregular RBC antigens other than Rh group like anti- Kell and anti- Duffy

by production of IgG which crosses placenta
IgG antibodies adhere to

the antigen site on the surface of erythrocytes causing hemolysis.
The excessive removal of circulatory RBCs leads to severe anemia and hypoxia.
Erythropoiesis results in hepatosplenomegaly.
Tissue hypoxia and hypoproteinemia results in cardiac and circulatory failure, with generalized odema and hydrops

leak into the maternal circulation.
Although leaks are common only 8%

are sensitized within 6 months after first del of ABO compatible preg.
16% are sensitized after second full term pregnancy of Rh positive ABO compatible pregnancy.
The risk of sensitization after ABO incompatible pregnancy is only 2%
Risk after spontaneous miscarriage is 3.5%
Risk after induce abortion is 5.5%
Risk after ectopic pregnancy is about 1%

anemia, requiring either phototherapy or no treatment.
25% have some degree

of hepatosplenomegaly and moderate anemia and progressive jundice culminating in kernicterus, neonatal death or severe handicap.
25% are hydropic and usually die in utero or in the neonatal period ( half of these the hydrops develops before 34 weeks gestation ).

risk
To predict whether or not the fetus is severely affected.
To

correct anemia and reverse hydrops by intrauterine transfusion.
To deliver the baby at the appropriate time, weighing the risks of prematurity against these of intrauterine transfusion.

antibody screening.
If indirect coombs test is positive, the father’s Rh

should be tested.
Serial maternal Anti D titers should be done every 2- 4 weeks.
If titer is less than 1/16 the fetus is not at risk.
If titer is more than 1/16 then severity of condition should be evaluated.

affected pregnancies
The levels of maternal hemolytic antibodies
Amniocentesis
Biophysical surveillance
Fetal

blood sampling

in amniotic fluid and fetal hematocrit.
The optical density deviation

at 450 nm measures the amniotic fluid unconjugated bilirubin.

being.
Placental size and thickness and hepatic size.
Fetal hydrops is easy

to diagnose when finding one or more of the following: Ascites, pleural effusion, pericardial effusion, or skin edema.
Doppler assessment of peak velocity of fetal middle cerebral artery proved to valuable in predicting fetal anemia

Median
80
70
60
50
40
30
20

20 25 30

35

A 1.5 MOM

B 1.29 MOM

Gestational Age (wks)

MCA peak velocity cm/sec

from Mari et al, NEJM 2000; 342:9-14

A = moderate-severe anaemia
B = mild anaemia
C = no anaemia

of fetal Hb, Hct, pH, reticulocytes and nucleated RBCs.
Risk fetal

exanguination and fetal death 1%.

vessel
Turbulance when injecting a small amount of saline into the

vessel.
Fetal blood has a higher mean corpuscular volume ( MCV usually 100 fL
An alkali elusion method can be used
Acid elution Betke-Kleihauer test

of ultrasound guided IPT resulted in dramatic improvement in survival

rates.
Fetoscopic intravascular route was renewed by Rodeck in 1981.
Percutaneous transfusion into the intrahepatic umbilical vein, Bang 1982.
Cordocentesis, Daffos 1983.
The use of cordocentesis for fetal top up transfusion by Berkowitz.

It has superior results, regarding survival rates, quality of survivors,

prolongation of gestation and the higher rate of vaginal delivery.
Access to the fetal circulation is extremely essential to avoid the lethal mistake of transfusing the Rh negative fetus or the nonanemic Rh positive fetus.
Decisions regarding transfusion and delivery are made on the basis of fetal blood group, Hb estimation and other hematologic parameters
. IVT results are better in the compromised hydropic fetus.

Gamma ray packed red blood cells with Hct 75%

Group O negative heterologous blood
Maternal blood

=(Gestation in weeks - 20) X 10

the basis of the fetal Hct achieved at the end

of the previous transfusion and the rate of fall in fetal Hct. The latter has been reported to be on average equal to 1% of Hct/day

Abruptio placetae.
Preterm labor.

related to intrauterine transfusion against the risk of prematurity.

1960s has led to a great reduction in isoimmunisation.
Following

delivery and caesarean section
Routine anti D administration at 28 weeks.
Following spontaneous and induced abortion.
Vaginal bleeding and threatened miscarriage.
Performing amniocentesis, CVS,
Abdomenal trauma and external cephalic version.

delivery.
This covers 30 ml of fetal blood leak into maternal

circulation.
If greater transplacental hemorrhage is suspected the dose should be tailored after Kleihauer- Betke test to determine the volume of hemorrhage.

through the cell membrane than fetal hemoglobin.
Maternal blood is

fixed on a slide with ethanol 80%, treated with citrate phosphate buffer.
After staining with hematoxylin and eosin the fetal cells will be stained while the adult cells appear like ghost cells.
No. of fetal cells/ No. of adult cells is equal to
fetal blood volume/ maternal blood volume.