Does this test have other names?
Genetic testing, karyotyping
What is this test?
This test looks for changes, or abnormalities, in the chromosomes that make up your
body's DNA, or genetic road map.
Your chromosomes are found in the inner part of your cells, called the nucleus. They
contain all the genes that have been passed down to you from your mother and father.
Each person normally has 23 pairs of chromosomes in each cell (23 pairs = 46 total
chromosomes). One of these pairs is called the sex chromosomes (X and Y). They determine
if you will be male or female. If you are male, you have an XY pair. If you are female,
you have an XX pair. The other 22 pairs are called autosomes, and are the same in
males and females.
Cells for chromosome analysis can come from a blood sample, from inside a bone (bone
marrow sample), from a swab of cells taken from inside your mouth, or from a sample
of your skin or hair. Cells can also be taken from the fluid that surrounds a baby
inside a mother's uterus. This is called an amniocentesis.
Cells taken for chromosome analysis are sent to a lab. Here they are prepared and
arranged in order from largest to smallest. By looking at your chromosomes under a
microscope and taking pictures of them, which is called karyotyping, lab specialists
may be able to tell whether or not you have any extra or missing chromosomes or pieces
Abnormalities in your chromosomes help healthcare providers diagnose many health conditions.
In some cases, your chromosomes can help your healthcare provider predict a health
problem before you even have symptoms. Chromosome studies done on a developing baby
inside a mother's womb may predict problems that a baby may be born with or develop
later in life.
Why do I need this test?
You may need this test for a variety of reasons, from helping to diagnose disease
to finding out whether you have any changes in your genes that may be passed on to
your children. Here are some reasons to have this test:
To help diagnose or plan treatment for a disease
To find out your risk of developing a disease you may have inherited
To find out whether you carry a genetic change that may be passed onto your children
To find out whether your unborn child may have a genetic problem
To diagnose a genetic problem in a newborn or young child
To find out why you are having trouble getting pregnant
To find out why you are having miscarriages, or losing a baby before birth
What other tests might I have along with this test?
Your healthcare provider may also order other types of genetic testing that look for
certain genes within your chromosomes. For example, you may have a test called Fluorescence
In Situ Hybridization (FISH) analysis, which looks at specific parts of your chromosomes.
You may also have a more detailed chromosome test, called a microarray. This type
of test looks at the chromosomes very closely for small extra or missing pieces. You
may also have a blood test to look for abnormal proteins that might be a sign certain
genes aren't working the way they should.
What do my test results mean?
Test results may vary depending on your age, gender, health history, the method used
for the test, and other things. Your test results may not mean you have a problem.
Ask your healthcare provider what your test results mean for you.
Normal chromosomes are reported as:
44 autosomes plus two X chromosomes for a woman (karyotype 46,XX)
44 autosomes plus one X and one Y chromosome for a man (karyotype 46,XY)
Your healthcare provider will get a report from the lab that explains any abnormalities
found in your or your child's chromosome analysis. A karyotype picture may also be
included in the report.
Your healthcare provider should arrange for you to talk with a certified genetic counselor
who can help you understand the results of this test.
How is this test done?
This test needs a sample of your cells. Your healthcare provider can get the cells
in many ways. These are some options:
Taking a blood sample by putting a needle into a vein in your arm.
Taking a blood sample from a newborn by making a small prick on the baby's heel.
Taking a blood sample from the umbilical cord of fetus.
Taking out a sample of cells from the spongy center of a bone, called the bone marrow.
Bone marrow cells can give healthcare providers important information about blood
cancers like leukemia and lymphoma.
Taking a sample of amniotic fluid by putting a long, thin needle through the pregnant
woman's skin and into the fluid that surrounds the growing fetus
Taking a small piece of tissue. This is called taking a biopsy.
Taking a swab of cells from inside your cheek.
Does this test pose any risks?
Each method of taking a sample carries certain risks. Some have more risks than others.
Ask your healthcare provider to discuss all the risks and benefits with you before
What might affect my test results?
Depending on how your test is done, certain things may affect your results. Ask your
healthcare provider to explain these possibilities to you.
How do I get ready for this test?
Some chromosome analysis tests, such as amniocentesis, bone marrow sampling, or a
tissue biopsy, do need special preparation. Ask your healthcare provider how you should
prepare for your test. Blood sampling or cheek swabs usually don't need any preparation.