Karyotype Genetic Test

A karyotype test is a type of genetic testing. It looks at the size, shape, and number of chromosomes in a sample of cells from your body. Chromosomes are tiny 'packages' in your cells that contain your genes.

Genes carry information, called DNA, that controls what you look like and how your body works. Normally, all your cells (except for egg and sperm cells) have a set of the same 46 chromosomes. The chromosomes are grouped into 23 pairs.

Each pair has two chromosomes, one coming from each parent. A karyotype test checks the chromosomes in your cells to: See whether you have a full set of 46 chromosomes. Having too many or too few chromosomes can cause serious problems with health, growth, and normal development, such as Down syndrome (extra chromosome 21),Turner syndrome (missing X chromosome), and various genetic disorders.; Look for changes in the structure of chromosomes, such as broken, missing, or extra parts.

These changes may cause a wide variety of problems depending on which chromosome is affected. But some changes in chromosomes don't cause problems.; Certain chromosome problems are present from birth, while others can develop in certain cells later in life. Those that develop later in life can cause specific types of cancer.

Why this test is done

The most common reason for getting a karyotype test is if you're planning to have children or are pregnant. These tests can tell you if you or your partner have abnormal chromosomes that you could pass on to a baby. Your provider may also order this test on your fetus to see if they have a genetic disorder, especially if:

• The pregnant parent is age 35 or older. The overall risk of genetic birth defects is small, but the risk increases after age 35.
• Either parent has a genetic disorder, a family history of a genetic disorder, or another child with a genetic disorder.
• The results of certain prenatal screening tests weren't normal.

You may also need a karyotype test if:

• You and/or your child have symptoms of a genetic disorder. Each type of genetic disorder has different symptoms. Karyotype testing may be needed to make a diagnosis.
• You've been diagnosed with certain cancers or blood disorders that often involve changes in chromosomes. These changes can affect how your disease will progress and which treatment will work best for you. Karyotype testing may be needed to help diagnose and treat conditions such as leukemia, lymphoma, multiple myeloma, and anemia.
• You have a family history of a chromosomal disorder and want to know your risk for developing the disorder.

How to prepare

What you have to do to prepare will depend on the type of test you're getting.

• For a CVS or amniocentesis, you may need to drink extra fluid and not urinate before your test so that your bladder is full.
• A blood test or cheek swab usually don't require any preparation.
• If you're having a bone marrow test, ask your provider for instructions about how to prepare.

Sample type

Blood

Other names for this test

genetic testing, chromosome testing, chromosome studies, cytogenetic analysis