What is Rh incompatibility?
If you are a mother with Rh incompatibility, there is a
substance in your baby's red blood cells that is not in your
blood cells. This substance is usually called the Rho(D)
factor. People who have the Rho(D) factor are Rh positive.
People who do not have it are Rh negative. Being Rh
negative or positive is something you inherit from your
parents, just like you inherit the color of your eyes or
hair.
While you are pregnant or delivering the baby, some of the
baby's red blood cells may come in contact with your blood.
Your body may then make antibodies to the Rho(D) factor.
This reaction is called sensitization. The antibodies may
cross the placenta and destroy the red blood cells in your
baby or any Rh-positive babies you have later. This
destruction of red blood cells is called hemolytic disease.
This disease can cause serious problems for the baby.
How does it occur?
Rh incompatibility happens only if you are Rh negative and
your baby is Rh positive. It does not happen if you are Rh
positive and your baby is Rh negative or if both of you are
negative or positive.
Usually you are not exposed to a baby's blood until you give
birth. This means that your first baby is not likely to be
affected by the incompatibility. However, large amounts of
the baby's blood often leak into the mother during delivery.
Your body might then make antibodies. This can cause
problems if you have another Rh-positive baby.
Sometimes the baby's blood may come in contact with your
blood before delivery. This might happen, for example,
during a miscarriage or abortion or after amniocentesis or
other similar tests.
If you are Rh negative and you got Rh-positive blood in a
transfusion, you may have developed antibodies that will
cause Rh incompatibility.
In most cases, development of antibodies can be prevented.
What are the symptoms
You will have no symptoms. The baby will have symptoms if
he or she develops hemolytic disease. The baby's red blood
cells will start to break down, causing anemia. The anemia
may cause yellow eyes and skin (jaundice), body swelling,
and breathing problems. The baby might die in the womb if
too much of the baby's blood is destroyed by the antibodies.
How is it diagnosed?
Blood tests are done to check for the Rho(D) factor to see
if you are Rh positive or negative. Blood tests also check
for antibodies against the Rho(D) factor. If you are Rh
negative, the baby's father should also be tested. If the
father's blood is Rh positive, the baby may inherit
Rh-positive blood from him. If both you and the father are Rh
negative, there will not be a problem because the baby will
also be Rh negative.
Some of the tests used to check for hemolytic disease and
its effects on the baby are:
- amniocentesis (a test of fluid around the baby)
- cordocentesis (removing blood from the baby's umbilical
cord)
- ultrasound scan
- nonstress test (a check of the baby's activity and heart
rate for a short time)
- blood tests
- biophysical profile (a check of the baby's movements,
heart rate, and brain waves).
How is it treated?
If you have already been sensitized by a previous birth,
your baby may have hemolytic disease before birth. Your
baby will be carefully checked with ultrasound scans and
amniocentesis. These tests will help your provider know
what treatment may be needed. For example, the baby may
need a blood transfusion in the womb before birth.
Sometimes early delivery by cesarean section (C-section) is
necessary.
If you have not been sensitized, you will have a shot of
Rh-immune globulin (RhoGAM) at about 28 weeks of pregnancy. If
you have not delivered the baby within 12 weeks of this
first shot, you will have a second shot. You may also be
given a shot within 72 hours after a birth (if the baby is
Rh positive), miscarriage, abortion, tubal (ectopic)
pregnancy, or amniocentesis.
RhoGAM contains antibodies to the Rho(D) factor. The
antibodies in the shot will destroy any red blood cells from
the baby that are in your blood. Then your body will not
make its own antibodies to the Rho(D) factor. If you have
the shot at 28 weeks and after delivery, sensitization will
be prevented and Rh incompatibility should not be a problem
during your next pregnancy.
It is important to have the RhoGAM shot in all cases when
the baby's blood could leak into your system. This
includes:
- during or after all pregnancies, including ectopic
pregnancies
- after early miscarriages
- after chorionic villus sampling or amniocentesis
- after external cephalic version (a procedure used to try
to change a baby's position in the womb before birth)
- after injury to your abdomen.
If you have a threatened miscarriage but do not actually
miscarry, you may also need a RhoGAM shot. Discuss this
with your health care provider.
How long will the effects last?
Sensitization usually does not happen until after the birth
of an Rh-positive baby. Therefore, in most cases Rh
incompatibility is not a problem during your first pregnancy
and delivery of an Rh-positive baby. However, later
pregnancies and deliveries might be affected unless you are
treated with RhoGAM.
Once you become sensitized, RhoGAM is not helpful. You will
stay sensitized, and the effects are usually worse with each
pregnancy.
What can be done to help prevent the problems of Rh
incompatibility?
This problem of pregnancy has not happened often since the
discovery of RhoGAM. RhoGAM can prevent sensitization. It
is given to Rh-negative women right after every delivery,
miscarriage, or abortion. It is also given to pregnant
Rh-negative women after amniocentesis, after any bleeding
episodes, and during the 7th month of pregnancy.


Disclaimer: This content is reviewed periodically and is subject to
change as new health information becomes available. The
information provided is intended to be informative and educational and is not a
replacement for professional medical evaluation, advice, diagnosis or
treatment by a healthcare professional.
HIA File WOM5311F.HTM Release 9.0/2006. Copyright © 2006 McKesson Corporation and/or one of its subdiaries. All Rights Reserved.
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