Karyotype Genetic Test
Reviewed
Also called: genetic testing, chromosome testing, chromosome studies, cytogenetic analysis
A karyotype test looks at the size, shape, and number of chromosomes in a sample of cells to see if you have a full set of 46 chromosomes, and to look for changes in chromosome structure that may cause health problems, growth issues, or genetic disorders. It is often used when planning to have children, during pregnancy, or to help diagnose certain cancers and blood disorders.
Specimen: For adults, children, and babies: blood (most common), buccal (cheek) swab, or bone marrow. For a fetus: amniotic fluid (amniocentesis) or chorionic villi (CVS).
Why this test may be ordered
- To check for chromosome problems in a fetus, especially if the pregnant parent is age 35 or older, if either parent has a genetic disorder or family history, or if prenatal screening results were not normal.
- To check yourself or family members for specific chromosome problems.
- To find out if abnormal chromosomes are causing infertility, frequent miscarriages, or stillbirths.
- To help diagnose and make treatment decisions for certain cancers and blood disorders such as leukemia, lymphoma, multiple myeloma, and anemia.
- To evaluate symptoms of a genetic disorder or to determine your risk if you have a family history of a chromosomal disorder.
Preparation and collection
For a blood test or cheek swab, no special preparation is needed. For amniocentesis or CVS, you may need to drink extra fluid and not urinate before the test so your bladder is full. For a bone marrow test, ask your provider for instructions.
Blood test, amniocentesis, chorionic villus sampling (CVS), buccal (cheek) swab, or bone marrow test
During amniocentesis or CVS, you may feel mild stinging or cramping. Both procedures have a slight risk of causing miscarriage. A blood test has very little risk; you may have slight pain or bruising at the needle site, but most symptoms go away quickly. A cheek swab has no risk. After a bone marrow test, you may feel stiff or sore where the sample was taken; serious risks are rare.
Understanding results
The results of a karyotype test look at the number, size, and shape of chromosomes in your cells. Normal results are sometimes called 'negative' and abnormal results are called 'positive'.
- Normal (negative): Your chromosomes appear typical: 46 chromosomes in 23 pairs, without any unusual changes in structure. Limitation: A normal result does not rule out all possible genetic or chromosome conditions. Next step: No further action is typically needed unless you have other risk factors or symptoms.
- Abnormal (positive): Unusual changes in the number or structure of chromosomes were found. Depending on the specific changes, this may indicate a condition such as Down syndrome (extra chromosome 21), Turner syndrome (missing X chromosome), or other genetic disorders. Some chromosome changes do not cause problems, but others can affect health, growth, and development. The results can also help diagnose certain cancers and blood disorders. Limitation: Additional testing may be needed to confirm the specific diagnosis and understand its implications. Next step: Talk with your provider to understand what the unusual changes mean for your health or your child's health. A genetic counselor can help you make informed decisions about treatment or management options.
- A normal result does not rule out all possible genetic or chromosome conditions.
- Additional testing may be needed to confirm the specific diagnosis and understand its implications.
- A blood test has very little risk; slight pain or bruising at the needle site, but symptoms usually go away quickly.
- A cheek swab has no risk.
- Amniocentesis and CVS are safe but have a slight risk of causing miscarriage.
What to do next
If you have received abnormal results or are considering testing, it may help to talk with a genetic counselor, who can provide information about how genetic conditions might affect you or your family and help with support services and informed decisions about treatment or management options.
- What does a normal result mean?
- What does an abnormal result mean?
- What specific chromosome changes were found in my sample?
- What health problems could these changes cause?
- Do I need further testing or a referral to a genetic counselor? What are my next steps?