Karyotype is a test to identify and evaluate the size, shape, and number of chromosomes in a sample of body cells. Extra, missing, or abnormal positions of chromosome pieces can cause problems with a person's growth, development, and body functions.

Why It Is Done

Karyotype is done to:

• Determine whether the chromosomes of an adult have an abnormality that can be passed on to a child.
• Determine whether a chromosome defect is preventing a woman from becoming pregnant or causing miscarriages.
• Determine whether a chromosome defect is present in a fetus. Karyotyping also may be done to determine whether chromosomal problems may have caused a fetus to be stillborn.
• Determine 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 determining the presence of the Y chromosome. This may be done when a newborn's sex is not clear.

How To Prepare

No special preparation is needed before having this test.

Talk to your health professional 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 a genetic test 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 your risk for having a child with an inherited (genetic) disease, such as sickle cell disease, cystic fibrosis, or hemophilia. A genetic counselor can help you make well-informed decisions. Ask to have genetic counseling before making a decision about a genetic test.