Incompatibility between an infant’s blood type
and mom’s can result in a severe anemia in the
developing baby.
Just as there are different blood groups, like A,
B, O, AB there are other blood factors that can
be on the red blood cells and it is these factors
(a type of protein) that if different than the
mothers that causes the problem. These factors
can be from the dad or from the mom receiving
a blood transfusion.
The most common factor is Rh but there are
many others than can cause the anemia. These
factors cause the mom to make antibodies
(chemicals) against the baby’s red blood cells
which destroys them causing the anemia.
Disease Impact on the Pregnancy
Routine testing in pregnancy will identify these
antibodies.
Your partner can be tested to see if he has the
factor to which you make the antibody.
If your partner has the factor, then the fetus
may also have it. If the fetus has the factor, then
your body may make antibodies that destroy
the fetal blood cells.
While we have tests that can detect almost of
all of the different blood factors, there is not
test for the Rh negative factor.
The most that can be known about a
person’s Rh status is if he has the gene,
we cannot tell if he has 1 or 2 genes for
Rh disease.
When 2 copies of the gene are present for a
factor, then the fetus will always have the
factor. If a man has only 1 copy of the gene for
the factor, then there is a 50% chance the fetus
will not inherit the factor from the male partner.
The amount of antibody will be measured and
followed through the pregnancy.
For most factors, the amount of antibody in a
woman’s blood stream is a reliable indicator of
the severity of disease.
If the levels of antibody increase, and
amniocentesis may be done
Amniocentesis is used to check for blood
break down in the fetus. When blood cells are
destroyed, a chemical called billirubin is made.
Billilrubin changes the color of amniotic fluid
and can be measured using special lab
techniques.
Amniocentesis can also be used to determine
the blood type of the fetus. It is about 95%
accurate.
If severe anemia is suspected, periumbilical
blood sampling (PUBS) may be performed.
This is done by a maternal fetal medicine
specialist with extra training in high risk
pregnancy and ultrasound.
PUBS refers to drawing blood out of the
umbilical cord of the unborn fetus.
The blood type of the fetus, and the blood
count can then be determined with 100%
accuracy.
If severe anemia is present, blood can be
transfused into the unborn fetus.
Fetuses born from women with this condition
often have special problems.
They are often born preterm (before 37 weeks)
They may be severely anemic at birth and need
blood tranfusions.
They may have massive break down of blood
cells after birth and need special lights to help
eliminate billirubin from their blood.
High levels of billirubin may cause mental
retardation.
Pregnancy Impact on Disease
The severity of disease usually worsens with
each pregnancy by the same partner.
Special Prenatal/ Birth/Neonatal considerations
Women with severe isoimmunization should be
cared for with the help of a maternal-fetal
medicine specialist.
If disease is severe, these fetuses should be
born at hosptils with full intensive care
nurseries.
Antenatal testing is used extensively if affected
pregnancies to make sure the fetus is remaining
healthy.
When properly treated, most babys do very
well and do not have long term complications.
Occasionally, pregnancies are lost despite the
best medical management, or there are long
term problems from the disease.
Issoimmunization does not pose a risk to the
mother.