Amniocentesis
Amniocentesis
What is amniocentesis?
To find out if a baby has a chromosome
Information
problem before birth, we test the fluid
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Amniocentesis (AM-nee-oh-sen-TEE-sis)
around the baby. This fluid is called amniotic
— or amnio for short — is a medical test
(am-nee-OT-ik) fluid.
for pregnant women. It is usually performed
between the 16th and 18th weeks of
The baby sheds some cells, with the baby’s
pregnancy to see if the baby has certain
chromosomes in them, into this fluid. Careful
conditions, such as Down syndrome.
testing of the fluid finds the cells and looks for
problems in them.
Amniocentesis is a genetic test. Genetic tests
are used to look for certain genetic diseases,
Brain and spine problems, such as open skull
chromosome problems, and birth defects.
(anencephaly) and open spine (spina bifida),
Your doctor and/or a genetic counselor can
also can be found by measuring the level of
help to determine which test or tests are right
AFP (alpha-fetoprotein) in the fluid.
for you. This depends on factors such as your
age, your family and medical history, and
How is amniocentesis done?
environmental exposures. Genetic testing
cannot answer all questions about the health
A sample of the fluid is taken with a thin
of your developing baby, but it can provide
needle. The needle is guided by ultrasound
information to help you and your partner
(see the UPMC patient education sheet
make informed decisions.
Ultrasound: Pelvic, Pregnancy, and Abdominal).
Ultrasound uses sound waves to produce a
“picture” of the baby. It appears as an image
Checking for chromosome
on a small TV screen (monitor). Ultrasound
problems
helps the doctor decide how far along the
Each cell of your body has chromosomes
pregnancy is. It shows if more than one baby
that carry the blueprint for your whole body.
is present. It also shows where the placenta is.
The chromosomes carry the traits (such as eye
For the ultrasound, you will lie on your back
or hair color) that you inherited from your
on a table in an exam room. A gel will be
mother and father. Normally, each cell
spread on your belly. The gel helps the sound
contains 46 chromosomes. Having too much
waves pass through your belly. You will
or too little chromosome material often
probably be able to see your baby’s image on
results in health problems.
the screen.
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AMNiOCENTESiS
A thin needle is placed through your belly and
Who should consider having
through the wall of your uterus. The needle
amniocentesis?
takes a small amount of amniotic fluid from
the sac surrounding the developing baby. The
A woman should consider having amnio if
ultrasound is used to show where the baby
she will be 35 or older at the time her baby is
and placenta are. That way the needle can be
due to be born. Any woman could have a child
with a chromosome disorder, but mothers who
University of
placed so it won’t touch the baby.
Pittsburgh
are older have a greater risk.
Amniocentesis, including ultrasound, takes
Medical Center
less than 1 hour. You will not have to stay in
A younger woman should consider
Information
amniocentesis if she:
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the hospital overnight.
• already has a child with a chromosome
After amnio
disorder, such as Down syndrome
You should take it easy the rest of the day but
• knows that she or her partner has a
may go back to your usual activity the next
chromosome disorder
day. You will be told to watch for any unusual
occurrence. If you have bleeding or loss of
Are there risks with amnio?
fluid through the vagina, severe cramping, or
a fever, call your doctor.
As with many medical procedures, there are
risks with amniocentesis. Recent studies
suggest that the risk of miscarriage is
How will i find out the results?
approximately 1 pregnancy loss in every 1,000
The fluid will be tested in a lab. Results from
procedures performed. Before agreeing to
the test are usually available in 10 to 14 days.
have amniocentesis and genetic testing, you
Ask your doctor when you should call his or
will be asked to sign a consent form that
her office for your results.
explains the risks involved.
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continued
AMNiOCENTESiS
Does amniocentesis identify all
birth defects?
No. It is important to remember that all couples
have a 2 to 3 percent risk of having a child with
a birth defect. This means that out of every 100
pregnancies, on average, 97 or 98 babies will
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have no birth defects, and 2 or 3 babies will
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Medical Center
have a birth defect. Many of these birth defects
are not due to a chromosome disorder. So
Information
for Patients
amniocentesis would not find them.
if an abnormality is found, what
are the options?
If a disorder is found, your doctor will explain
your options. At UPMC, counseling and
support are available to help the couple make an
informed decision. Several medical options are
available, including referral to experts who are
familiar with the treatment and management of
specific conditions.
For more information
If you have additional questions or think you
may want amniocentesis, please call the UPMC
Center for Medical Genetics at 412-641-4168
or 1-800-454-8155.
This educational material was developed by a team of women’s health care experts throughout
Pittsburgh, PA, USA
UPMC, including Magee-Womens Hospital, a National Center of Excellence in Women’s Health
www.upmc.com
as designated by the U.S. Department of Health and Human Services.
For help in finding a doctor or health service that suits your needs, call the UPMC Referral Service
at 412-647-UPMC (8762) or 800-533-UPMC (8762). Select option 1.
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This information is not intended to be used as a substitute for professional medical advice, diagnosis, or treatment. You should not rely entirely on this information for
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