Chromosome Analysis

What is chromosome analysis?

Chromosome analysis (also called a karyotype) evaluates the number, size, and structure of a person’s chromosomes. Human cells are supposed to have 46 chromosomes, or 23 pairs. In the first 22 pairs, the chromosomes should match up in size and shape. The last pair are the sex chromosomes and determine a person’s genetic sex. Females typically have two copies of the X chromosome, while males typically have one X and one Y chromosome.

Though 46 chromosomes are expected, anyone can be born with extra or missing chromosomes, or with changes in the size and structure of their chromosomes. Individuals with chromosome differences can have face different medical and reproductive concerns.

Though a chromosome analysis can assess for a number of conditions, the test cannot screen for every known genetic disorder. Depending on the reason for genetic testing, there may be other tests recommended.

I am thinking about having a pregnancy in the future. Should I consider a chromosome analysis?

Chromosome analysis is a blood test and results typically take 2-4 weeks. Though it is not routinely offered, it may be recommended for the following individuals:

• There is a personal or family history of 2 or more miscarriages
• There is a personal or family history of chromosome disorders, such as Down syndrome
• There is a known family history of a translocation or other chromosome condition

Usually both biological parents are tested, since chromosome abnormalities can come from either parent.  When the reason for testing is because of family history, it may be recommended that only one individual is tested.

What would results mean for a current or future pregnancy?

If a chromosome abnormality is found in a parent, there may be increased risks for their offspring. The exact risks would depend on the chromosome(s) involved. Genetic testing would be available for the pregnancy. Additionally, some families may consider in-vitro fertilization (IVF) with preimplantation genetic testing.

If the results are normal, a chromosome disorder would not be expected to affect your odds of a successful pregnancy in the future. It is important to know that a negative chromosome analysis does not eliminate the chance for a sporadic chromosome condition and prenatal testing would still be offered.

Does a chromosome analysis look at all genetic conditions?

Though a chromosome analysis can assess for a number of chromosome conditions, the test cannot screen for every known genetic disorder. Depending on your personal or family history, there may be other tests recommended.

Where can I learn more?

When considering chromosome analysis, an appointment with a genetic counselor can be helpful. To schedule an appointment, please call 713-486-9302.