What Is Genetic Testing?

Genetic testing looks for changes in someone’s genes. Gene changes can cause genetic illnesses (also called genetic disorders). They can also make someone more likely to have certain medical problems (like some cancers). Some genetic illnesses can run in families.

People get genetic testing to see if they have genetic changes themselves or if they can pass on genetic changes to their children. Genetic counselors help people decide what tests to get and understand what the tests mean.

How Is Genetic Testing Done?

Genetic tests can be done on small samples of blood or saliva (spit). In pregnant women, genetic testing can be done on amniotic fluid (through amniocentesis) or the placenta (through chorionic villus sampling). Testing can also be done on an embryo during in vitro fertilization (IVF). Usually, it takes a few weeks for test results to be ready.

What Kinds of Genetic Tests Are There?

There are several different kinds of genetic tests. Some look at only a few genes and others look at the whole chromosome. Some look at special proteins called enzymes. Doctors and genetic counselors help families choose the right test.

What Can Genetic Testing Find?

Depending on the test, doctors can find if someone has an illness, is at risk for an illness, and/or is a carrier for an illness. A carrier doesn’t have the illness, but can pass the gene change to their children.

Genetic testing usually can be done if the genetic changes for an illness are known. For example, testing can be done for:

• cystic fibrosis
• Tay-Sachs disease
• sickle cell disease
• Down syndrome
• spina bifida
• Turner syndrome
• von Willebrand Disease
• albinism
• Duchenne muscular dystrophy

In some cases, it also can show how a person will respond to certain medicines, or if they are more likely to get some types of cancer.

Who Might Want to Get Genetic Testing?

People get genetic testing for many reasons. Pregnant women often get genetic testing on their blood as part of their regular prenatal care. 

Someone might get genetic testing to:

• Learn if they have a genetic illness that runs in their family.
• See if a current pregnancy is affected by a genetic illness.
• Learn what the risk is for a future pregnancy to be affected by a genetic illness.
• See if they are a carrier for a genetic illness.
• Guide treatment plans for certain genetic illnesses.
• See if a child has a genetic illness.

People with a higher risk for having a child with a genetic illness may want genetic testing. This includes:

• families with genetic illnesses in close relatives
• parents who already have a child with a genetic illness
• couples who plan to start a family and one of them or a close relative has a genetic illness
• pregnant women over age 34 or who have an abnormal prenatal screening test or amniocentesis
• women who have had two or more miscarriages, or delivered a stillborn baby with physical signs of a genetic disorder

How Does Someone Get Genetic Testing?

If someone decides they want genetic testing, they meet with a genetic counselor. The counselor can help them decide what tests to get and to understand the test results. They can talk about different options and offer support and resources.

After talking to a genetic counselor, some people decide not to do genetic testing. It may be too expensive or cause too much worry. Othes might decide not to do it because they don’t want to know or it’s not going to change any decisions they make. There is no right or wrong answer about who should get genetic testing.

What Else Should I Know?

Scientists are learning more and more about genetics. A worldwide research project called The Human Genome Project created a map of all human genes. It shows where the genes are located on the chromosomes. Doctors can use this map to find and treat or cure some kinds of genetic disorders. There is hope that treatments for many genetic disorders will be developed in the future.