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.
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 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