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If you are
Rh-negative, your red blood cells do not have a marker
called Rh factor on them. Rh-positive blood does have this marker. If your
blood mixes with Rh-positive blood, your
immune system will react to the Rh factor by making
antibodies to destroy it. This immune system response is called Rh
Rh sensitization can occur during pregnancy if you are
Rh-negative and pregnant with a developing baby (fetus) who has
Rh-positive blood. In most cases, your blood will not mix with your baby's
blood until delivery. It takes a while to make antibodies that can affect the
baby, so during your first pregnancy, the baby probably would not be
But if you get pregnant again with an Rh-positive baby, the
antibodies already in your blood could attack the baby's red blood cells. This
can cause the baby to have
jaundice, or more serious problems. This is called
Rh disease. The problems will tend to get worse with
each Rh-positive pregnancy you have.
Rh sensitization is one reason it's important to see your doctor
in the first trimester of pregnancy. It doesn't cause any warning symptoms, and
a blood test is the only way to know you have it or are at risk for it.
Rh sensitization during pregnancy can only happen if a woman has
Rh-negative blood and only if her baby has Rh-positive blood.
If you have Rh-negative blood, your doctor will probably treat
you as though the baby's blood is Rh-positive no matter what the father's blood
type is, just to be on the safe side.
All pregnant women get a blood test at their first prenatal visit
during early pregnancy. This test will show if you have Rh-negative blood and
if you are Rh-sensitized.
If you have Rh-negative blood but are not
If you are Rh-sensitized, your doctor will
watch your pregnancy carefully. You may have:
If you have Rh-negative
blood but are not Rh-sensitized, your doctor will give you one or more shots of
Rh immune globulin (such as RhoGAM). This prevents Rh sensitization in about 99
women out of 100 who use it.footnote 1
You may get a shot of Rh immune globulin:
The shots only work for a short time, so you will need to repeat
this treatment each time you get pregnant. (To prevent sensitization in future
pregnancies, Rh immune globulin is also given when an Rh-negative woman has a
miscarriage, abortion, or ectopic pregnancy.)
The shots won't work if you are already Rh-sensitized.
If you are Rh-sensitized, you will have regular testing to see
how your baby is doing. You may also need to see a doctor who
specializes in high-risk pregnancies (a perinatologist).
Treatment of the baby is based on how severe the loss of red
blood cells (anemia) is.
In the past, Rh sensitization was often deadly for the baby. But
improved testing and treatment mean that now most babies with Rh disease
survive and do well after birth.
Learning about Rh sensitization during pregnancy:
Living with Rh sensitization:
Rh sensitization can occur when a person with
Rh-negative blood is exposed to Rh-positive blood.
Most women who become sensitized do so during childbirth, when their
blood mixes with the Rh-positive blood of their fetus. After being exposed, a mother's
immune system produces
antibodies against Rh-positive red blood cells.
The minimum amount of blood mixing that causes sensitization
is not known. But many women become sensitized during pregnancy or
childbirth after being exposed to as little as 0.1 mL of Rh-positive fetal blood.footnote 1 Fortunately, Rh sensitization
can almost always be prevented with the
Rh immune globulin injection.
When an Rh-negative person's immune system is first exposed to
Rh-positive blood, it takes several weeks to develop immunoglobulin M, or IgM,
antibodies. IgM antibodies are too large to cross the
placenta. So the Rh-positive fetus that first
triggers maternal sensitization is usually not harmed.
A previously Rh-sensitized immune system rapidly reacts to
Rh-positive blood, as during a second pregnancy with an Rh-positive fetus.
Usually within hours of Rh-positive blood exposure, smaller immunoglobulin G,
or IgG, antibodies are formed. IgG antibodies can cross the placenta and
destroy fetal red blood cells. This causes
Rh disease, which is dangerous for the fetus.
Some Rh-negative people never become sensitized, even after
exposure to large amounts of Rh-positive blood. The reason for this is not
If you are already
Rh-sensitized or become Rh-sensitized while pregnant,
you will not have any unusual symptoms.
Fetal problems from Rh sensitization are detected with
Doppler ultrasound testing and sometimes with
amniocentesis. It is possible, though, that a fetus
with severe Rh disease will move less frequently than it did earlier in the
conditions with symptoms similar to Rh sensitization
include other blood type incompatibility problems and fetal infections.
Unless you are given
Rh immune globulin just before or after a high-risk event, such as
ectopic pregnancy, or childbirth, you have a chance of
becoming sensitized to an Rh-positive fetus's blood.
If you have been Rh-sensitized in the past, you must be closely
watched during any pregnancy with an Rh-positive partner, because
your fetus is more likely to have Rh-positive blood. In response to an
Rh-positive fetus, your immune system may quickly develop IgG antibodies, which
can cross the placenta and destroy fetal red blood cells. Each subsequent
pregnancy with an Rh-positive fetus may produce more serious problems for the
fetus. The resulting fetal disease (called Rh disease,
hemolytic disease of the newborn, or erythroblastosis
fetalis) can be mild to severe.
If you have been Rh-sensitized in the past, an Rh-negative fetus
cannot trigger an immune reaction.
Rh sensitization can occur when a person with
Rh-negative blood is exposed to Rh-positive blood.
During pregnancy, an Rh-negative woman can become
sensitized if she is carrying an Rh-positive
Things that increase the risk of blood mixing and sensitization
during pregnancy include:
Although rare, Rh sensitization has been known to occur after
needle sharing between intravenous drug users. Transfusing Rh-positive blood in
an Rh-negative person can also trigger sensitization. But this is
extremely rare, because blood is always tested prior to transfusion.
Your pregnancy will be closely monitored. Discuss possible
symptoms early in pregnancy with your doctor. Repeated diagnostic
testing will be needed to watch the fetus.
Call your doctor immediately
if you note a decrease in your fetus's movement after 24 to 26 weeks of
Call your doctor immediately
A woman who may have problems with
Rh incompatibility or sensitization can be treated
If you test positive for Rh sensitization, your health care
system or health professional may want you to be followed and treated by a
perinatologist or an obstetrician who can easily call in a
To prepare for your appointment, see the topic Making the Most of Your Appointment.
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.
All pregnant women have an
indirect Coombs test during early pregnancy.
If you are already Rh-sensitized or become sensitized while
pregnant, close monitoring is important to determine whether your fetus is
If your blood is Rh-negative and you have been
sensitized to Rh-positive blood, you now have
antibodies to Rh-positive blood. The antibodies kill
Rh-positive red blood cells. If you become pregnant with an Rh-positive baby
(fetus), the antibodies can destroy your fetus's red blood cells. This can
If you are already Rh-sensitized and are pregnant, your treatment
will focus on preventing or minimizing fetal harm and on avoiding early
Treatment options depend on how well or poorly the fetus is
If you are an
Rh-negative woman and you have conceived with an
Rh-negative partner, you are not at risk of
Rh sensitization during pregnancy. (Most health
professionals treat all Rh-negative pregnant women as
though the father might be Rh-positive.)
If you are already sensitized to the Rh factor, your pregnancy
will need to be closely monitored to prevent fetal harm. For more information
on fetal and newborn treatment, see Treatment Overview.
If you are unsensitized
Rh-negative, treatment focuses on preventing Rh sensitization during pregnancy
Rh immune globulin (such as RhoGAM) is a highly effective treatment for
Rh immune globulin is also needed within 72 hours after vaginal bleeding, a
partial molar pregnancy,
ectopic pregnancy, or abortion.
Rh immune globulin is effective in preventing
Rh sensitization.footnote 1 Rh
immune globulin contains Rh
antibodies that have been purified from human donors.
This treatment prevents an unsensitized Rh-negative mother from making
antibodies against her fetus's Rh-positive blood.
If an affected fetus younger than 34 weeks needs to be delivered,
corticosteroid medicine (betamethasone or dexamethasone) may be given to the mother to speed fetal lung
development before a premature birth.
intrauterine fetal blood transfusion is sometimes used
to supply healthy blood to a fetus with severe
hemolytic disease of the newborn (also called Rh
disease or erythroblastosis fetalis).
blood transfusion or exchange transfusion is
sometimes given to a newborn to treat severe
jaundice related to Rh disease.
American College of Obstetricians and Gynecologists (1999, reaffirmed 2010). Prevention of Rh D alloimmunization. ACOG Practice Bulletin No. 4. Obstetrics and Gynecology, 93(5): 1–7.
Other Works Consulted
Moise KJ Jr (2008). Management of rhesus alloimmunization in pregnancy. Obstetrics and Gynecology, 112(1): 164–176.
Roman AS (2013). Late pregnancy complications. In AH DeCherney et al., eds., Current Diagnosis and Treatment Obstetrics & Gynecology, 11th ed., pp. 250–266. New York: McGraw-Hill.
U.S. Preventive Services Task Force (2004). Screening for Rh (D) incompatibility. Rockville, MD: Agency for Healthcare Research and Quality. Available online: http://www.uspreventiveservicestaskforce.org/uspstf/uspsdrhi.htm
ByHealthwise StaffPrimary Medical ReviewerSarah Marshall, MD - Family MedicineKathleen Romito, MD - Family MedicineE. Gregory Thompson, MD - Internal MedicineAdam Husney, MD - Family MedicineSpecialist Medical ReviewerWilliam Gilbert, MD - Maternal and Fetal Medicine
Current as ofMay 30, 2016
Current as of:
May 30, 2016
Sarah Marshall, MD - Family Medicine & Kathleen Romito, MD - Family Medicine & E. Gregory Thompson, MD - Internal Medicine & Adam Husney, MD - Family Medicine & William Gilbert, MD - Maternal and Fetal Medicine
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