Test Overview
Karyotype is a test to identify and evaluate the size, shape, and number of chromosomes, Opens dialog 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
Karyotyping, Opens dialog
is done to:
- 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 causing miscarriages, Opens dialog.
- Find out whether a chromosome defect is present in a fetus, Opens dialog. Karyotyping also may be done to find out whether chromosomal problems may have caused a fetus to be stillborn.
- Find out the cause of a baby's birth defects or disability.
- Help determine the appropriate treatment for some types of cancer.
- 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.
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, Opens dialog. 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, Opens dialog. A genetic counselor can help you make well-informed decisions. Ask to have genetic counseling, Opens dialog before making a decision about a karyotype test.
How It Feels
Karyotype testing is usually done using a blood sample from a vein. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
Risks
Blood sample from a vein
There is very little chance of having a problem from this test. A small bruise may form at the site.
Results
Karyotype is a test to identify and evaluate the size, shape, and number of chromosomes, Opens dialog in a sample of body cells.
Results of a karyotype test are usually available within 1 to 2 weeks.
Karyotype
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Normal:
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- There are 46 chromosomes that can be grouped as 22 matching pairs and 1 pair of sex chromosomes (XX for a female and XY for a male).
- The size, shape, and structure are normal for each chromosome.
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Abnormal:
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- There are more than or fewer than 46 chromosomes.
- The shape or size of one or more chromosomes is abnormal.
- A chromosome pair may be broken or incorrectly separated.
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Credits
Current as of: April 30, 2024