If you are pregnant, you will have your first prenatal tests during
trimester. Every woman
has her blood tested at the first prenatal visit to see what her blood type is. If your blood is
Rh-negative, it will also be tested for
antibodies to Rh-positive blood. If you have
antibodies, that means that you have been
sensitized to Rh-positive blood. The antibodies can
now kill Rh-positive red blood cells.
If you are Rh-negative and your partner is Rh-positive,
your fetus is likely to be Rh-positive.
If you are pregnant or have
miscarried, or if you have had an elective abortion, a
partial molar pregnancy, or an
ectopic pregnancy, you will need testing to see if you
have been sensitized to Rh-positive blood.
At the first prenatal visit, your blood is
tested to see if you have been previously sensitized to Rh-positive blood. If
you are Rh-negative and test results show that you are not sensitized, a repeat
test may be done between 24 and 28 weeks.
If test results at 28
weeks show that you have not been sensitized, no additional tests for
Rh-related problems are done until delivery (barring complications such as
placenta abruptio). You will also have a shot of Rh
immune globulin. This lowers your chances of being sensitized during the last
weeks of your pregnancy.
If your newborn is found to be
Rh-positive, your blood will be screened again at delivery with an indirect
Coombs' test to see if you have been sensitized during late pregnancy or
childbirth. If you have not been sensitized, you will have another shot of Rh
If you are sensitized to the Rh factor
If you are already Rh-sensitized or become sensitized while
pregnant, close monitoring is important to determine whether your fetus is
If possible, the father will be tested to see
if the fetus could be Rh-positive. If the father is Rh-negative, the fetus is
Rh-negative and is not in danger. If the father is Rh-positive,
other tests may be used to learn the
fetus's blood type. In some medical centers, the mother's blood can be tested
to learn her fetus's blood type. This is a new test that is not widely
indirect Coombs' test is done periodically during your
pregnancy to see if your Rh-positive antibody levels are increasing. This is
the typical course of treatment for most sensitized women during
Doppler ultrasound of blood flow in the brain shows
fetal anemia and how bad it is. At a medical center with Doppler experts, this
test can give you the same anemia information as
amniocentesis, without the risks.3
Fetal blood sampling (cordocentesis) may be done to
directly assess your fetus's health. This procedure is used on a limited basis,
usually for monitoring known sensitization problems (as when a mother has had
previous fetal deaths, or when other testing has shown signs of fetal
Electronic fetal heart monitoring
(nonstress test) may be done in the third trimester to check your fetus's
condition. Unusual fetal heart rhythms detected during a nonstress test may be
a sign that the fetus has
anemia related to the sensitization.
Fetal ultrasound testing can be used as a pregnancy
progresses to detect sensitization problems, such as fetal fluid retention (a
sign of severe Rh disease).
WebMD Medical Reference from Healthwise
October 20, 2011
This information is not intended to replace the advice of a doctor.
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