Prenatal Diagnostic Tests

I Have My Test Results Is Testing Right for Me?

Prenatal Diagnostic Tests

What Are Prenatal Diagnostic Tests?

  • Amniocentesis and CVS are the two most common prenatal diagnostic procedures. Amniocentesis is usually done at 15 to 20 weeks of pregnancy. CVS is usually done at 10 to 13 weeks of pregnancy.
  • Amniocentesis and CVS are used to get a sample of cells to look directly at the baby's chromosomes. Both tests can accurately diagnose or rule-out most chromosome abnormalities, like Down syndrome.
  • Some genetic diseases, like cystic fibrosis and Tay-Sachs disease, can be diagnosed with amniocentesis or CVS. These disorders are caused by a single gene mutation. This testing has to be special ordered. It is usually done when the parents know they are at-risk based on previous carrier testing or a family history.
  • Amniocentesis and CVS have some risks. These risks depend on the experience of the doctor doing the procedure. The risk of miscarriage with CVS is less than 1 in 100 (less than 1%). The risk of miscarriage with amniocentesis is about 1 in 300 to 1 in 500 (or 0.2% to 0.33%).
  • No prenatal test can find all birth defects, forms of mental retardation, or genetic disorders.
Next: Learn: What Is a Chromosome Abnormality?

I got results from my CVS or amniocentesis. How accurate are they?

Prenatal diagnostic tests (CVS and amniocentesis) routinely check for chromosome abnormalities in a pregnancy. Amniocentesis also checks for spina bifida.

The results of these tests are more than 99% accurate. There is usually no need to repeat testing.

  • When chromosome results are normal, that means that the developing baby does not have Down syndrome or another chromosome problem that can be found with this test. However, a normal result doesn't rule out all genetic problems in a pregnancy. A lot of genetic conditions are caused by smaller changes that aren't part of this test. Individual genes aren't tested unless there is a known reason, like if both parents are carriers of a condition or there is a family history of a genetic condition.
  • When chromosome results are abnormal, that means that the developing baby has a change in the chromosomes. Down syndrome is the most common chromosome abnormality, but there are many others. Chromosome abnormalities can cause problems in health and development health problems that range from mild to severe. What results could mean for the pregnancy or for the child after birth will depend on exactly what chromosome abnormality was found. It may not be possible to predict exactly how a chromosome abnormality will affect a person, but your doctor or genetic counselor can tell you what is known about other people with the same change.

My results weren't normal. What does it mean? What should I do next?

Getting news that a chromosome abnormality was found in your pregnancy is difficult. It's normal for parents to have a wide range of reactions to the news, and all of those reactions are likely to be very normal. It often takes time to understand the results, process feelings, and make decisions about your next steps.

Talking to an expert can be helpful to learn more about your results and what they mean. You should talk to your doctor or a genetic counselor to review your results in detail.

Here are some questions you might ask:

  • What chromosome abnormality was found?
  • How does this chromosome abnormality affect people?
  • What are my options for the pregnancy?
  • Are there other tests that should be done?
  • Should we meet with any other doctors that may be familiar with this condition?
  • Does this diagnosis change my prenatal care or plans for delivery?