What is a Karyotype?
What is a Karyotype?
A karyotype is an individual's collection of chromosomes. 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.
How is this test done?
For adults, a simple blood draw can test for this. Karyotyping can also be performed during pregnancy:
Chorionic villus sampling (CVS): Doctors use a long needle to remove a small sample of your baby’s cells from the chorionic villi, which are tissues that are found within the placenta (the organ that forms within your womb to nourish your growing baby). The cells are then sent to the lab.
Amniocentesis. Doctors get samples of your baby’s cells by taking a small amount of amniotic fluid (the liquid that surrounds your baby in the womb) with a long needle they stick through your abdomen. Again, the cells are sent to a lab, where they will be studied. You can have it done between 15 and 20 weeks. There is a chance of miscarriage, although it’s a smaller chance than with CVS. It happens to just 1 out of every 200 women who have the procedure.
What does it test for?
Humans have 46 chromosomes (23 pairs). Babies inherit 23 from their mother and 23 from their father.
Sometimes, babies have an extra chromosome, a missing chromosome, or an abnormal chromosome. Karyotype tests will determine if any of these have happened with your baby. The most common things that doctors look for with karyotype tests include:
Down syndrome (trisomy 21). A baby has an extra, or third, chromosome 21. This affects how the baby looks and learns.
Edwards syndrome (trisomy 18). A baby has an extra 18th chromosome. Babies usually have many problems, and most don’t survive more than a year.
Patau syndrome (trisomy 13). A baby has an extra 13th chromosome. Babies usually have heart problems and severe mental impairment. Most won’t live more than a year.
Klinefelter syndrome. A boy baby has an extra X chromosome (47XXY). He may go through puberty at a slower pace, and he may not be able to have his own children.
Turner syndrome. A girl baby has a missing or damaged X chromosome. It causes heart problems, neck problems, and short height.