Karyotype is a test to identify and evaluate
the size, shape, and number of
chromosomes in a sample of body cells. Extra or missing chromosomes, or abnormal positions of chromosome pieces, can cause problems with a person's
growth, development, and body functions.
Why It Is Done
- Find out whether the chromosomes of an adult
have a change that can be passed on to a child.
- Find out
whether a chromosome defect is preventing a woman from becoming pregnant or is
- Find out whether a
chromosome defect is present in a
fetus. Karyotyping also may be done to find out
whether chromosomal problems may have caused a fetus to be
- Find out the cause of a baby's birth defects or
- Help determine the appropriate treatment for some types
- Identify the sex of a person by checking for the presence
of the Y chromosome. This may be done when a newborn's sex is not clear.
How To Prepare
You do not need to do anything before you have this test.
Talk to your doctor about any concerns you have
about the need for the test, its risks, or how it will be done. To help you
understand the importance of this test, fill out the
medical test information form(What is a PDF document?).
Since the information obtained from
karyotyping can have a profound impact on your life, you may want to see a
doctor who specializes in genetics (geneticist) or a
genetic counselor. This type of counselor is trained
to help you understand what karyotype test results mean for you, such as your
risk for having a child with an inherited (genetic) condition like
Down syndrome. A genetic counselor can help you make
well-informed decisions. Ask to have
genetic counseling before making a decision about a
How It Is Done
Karyotype testing can be done using
almost any cell or tissue from the body. A karyotype test usually is done on a
blood sample taken from a vein. For testing during pregnancy, it may also be
done on a sample of
amniotic fluid or the
Blood sample from a vein