Karyotype Test

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 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, Opens dialog or the placenta, Opens dialog.

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

For this type of test, cells are collected from the fetus using amniocentesis, Opens dialog or chorionic villus sampling, Opens dialog.

Cell sample from bone marrow

Bone marrow aspiration, Opens dialog may be used for a karyotype test.

Watch

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.