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
Karyotyping 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.
- 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 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. 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 karyotype test.
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 placenta.
Blood sample from a vein
A health professional uses a needle to take a blood sample, usually from an arm.
Cell sample from a fetus
Cell sample from bone marrow
Bone marrow aspiration may be used for 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.
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.
Karyotype is a test to identify and evaluate the size, shape, and number of chromosomes in a sample of body cells.
Results of a karyotype test are usually available within 1 to 2 weeks.