Prenatal Genetic Testing

There are many prenatal genetic testing options available today that can provide information about genetic conditions or birth differences in a baby.

Is genetic testing right for me?
The decision to undergo prenatal genetic testing, and which test to choose, is your choice. It depends on what the information will mean for your family. Here are some things to consider:

  • Will the information from testing be useful to you?
    -Would you prefer to know before baby is born if they will have a specific genetic condition or birth difference?
    -Would you prefer to wait until after birth to know this information?
  • How would you use the information obtained from the testing?
    -Will this information help you to better prepare for having a child with a specific genetic condition or birth difference?
    -Would this information change your pregnancy management or delivery plans?
    -Would this information change your decision about the pregnancy?
  • Will normal results help to ease worries you may have about the pregnancy?
  • Will the testing process cause you more worries during the pregnancy?

What prenatal genetic testing options are available?
Prenatal genetic testing is your choice. Some women would prefer “yes or no” answers and since screening tests cannot provide that, they may choose to go straight to a more definitive test. Or, they may consider a diagnostic test after having a screening test that suggests a higher chance of a genetic condition in their baby.

Prenatal genetic tests can be put into two categories:

1) Screening tests: include blood draws such as Maternal Serum Screening, Prenatal Cell-free DNA screening, carrier screening and ultrasound. In general, screening tests pose no risk to the baby, however they only tell you if the chance of a genetic condition or birth defect is higher or lower and do not give you “yes or no” answers.

2) Diagnostic tests: such as amniocentesis and chorionic villus sampling (CVS) can provide definitive, “yes or no”, results, however these tests involve some risk, including a chance of miscarriage.

Prenatal cfDNA Screening

Prenatal cell-free DNA screening is an optional prenatal blood test that screens for certain genetic conditions. It can be performed as early as 10 weeks of pregnancy. Cell-free DNA screening goes by many different names including Noninvasive Prenatal Testing (NIPT) or Noninvasive Prenatal Screening (NIPS). You may have heard it referred to as the new gender test, or be familiar with specific test brand names (Harmony™, MaterniT21®, verifi®, Panorama™, etc.)

Our blood contains fragments of our DNA known as cell-free DNA. When a woman is pregnant, her blood also contains DNA fragments from the placenta that has a genetic makeup that is usually identical to that of the developing baby. By analyzing this DNA in mom’s blood, it can be determined if there is an increased or decreased chance for certain genetic conditions in the baby. This test uses the latest technology and is currently the most accurate screening testing available.

What does cell-free DNA Screening Test For?
If the pregnancy is at high risk or low risk for:

  • Down syndrome
  • Trisomy 18
  • Trisomy 13
  • Differences with X and Y (gender) chromosomes

Not all labs screen for the same conditions.  It is not always possible to know before a child is born how much their health will be affected. It is important to know that cell-free DNA screening cannot detect all genetic conditions or birth defects. No test can guarantee the birth of a healthy baby.

How Certain are Cell-free DNA Screening Results?
Prenatal cell-free DNA screening is a screening test that can determine if the chance of certain genetic conditions in a pregnancy is higher or lower. Since cell-free DNA screening is not a diagnostic test, it cannot give you “yes” or “no” answers. It cannot detect all genetic changes that could cause health problems. Normal results do no guarantee and healthy pregnancy or baby.

If a result indicates a high or increased chance, then a diagnostic test such as amniocentesis, if desired, can be performed to determine whether the baby really has the condition or not. A low-risk result means the possibility the baby has the genetic condition is lower, but not zero. Additional follow-up apart from standard pregnancy management is not required unless otherwise indicated. The possibility for false positives and false negatives exists.

In rare circumstances, results cannot be obtained. Depending on a variety of factors, a blood redraw may or may not be requested. If a redraw is requested, this is done at no additional charge. A repeat sample does not always return a result. 

What are the Risks Associated with cell-free DNA Screening?
Cell-free DNA screening is performed on a sample of a pregnant woman’s blood. While there is no risk for pregnancy complications such as miscarriage, it is important to think about what these test results may mean for you. Most of the time the test will come back with a low chance for a genetic condition and many women feel relief based on these results. However, if the test indicates a higher chance of a genetic condition it may create worry and uncertainty about what to do next.

How to Decide About cell-free DNA Screening?
Decisions about genetic testing in your pregnancy should be based on your own beliefs, values, needs and personality. 

Some insurance companies do not cover this testing and some families may be responsible for the cost of the testing. You can contact your insurance company of the lab providing the test for more information.

Carrier Screening

Carrier screening is a type of genetic test that can tell you whether you carry a gene for certain genetic disorders. For some genetic disorders, it takes two genes for a person to have the disorder. A carrier is a person who has only one gene for a disorder. Carriers usually do not have symptoms or have only mild symptoms. Because they often do not know that they have a gene for a disorder, they can pass the gene on to their children. Carrier screening can help you find out the chances of having a child with a genetic disorder. If you screen positive, we recommend screening for your partner to determine potential pregnancy risk. There are larger carrier screen panels which can be ordered following genetics counseling.

What Does Carrier Screening Test For?
If the mother is a carrier of a gene for the following disorders:

  • Cystic Fibrosis
  • Spinal Muscular Dystrophy (SMA)
  • Fragile X Syndrome
  • Duchenne Muscular Dystrophy (DMD)

What are the Risks Associated With Carrier Screening?
Carrier screening is performed on a sample of a pregnant woman’s blood. While there is no risk for pregnancy complications such as miscarriage, it is important to think about what these test results may mean for you. 

How Certain are Carrier Screening Results?
No test is perfect. In a small number of cases, test results can be wrong. Also, because carrier screening looks for only a limited number of genes, it is possible that you are a carrier of a genetic disorder even if your test results are negative

Amniocentesis

Amniocentesis tests for certain genetic conditions and birth defects. It’s optional and usually performed at approximately 15 to 20 weeks at a doctor’s office that specializes in doing this procedure. Using ultrasound as a guide, a very thin needle is inserted through the abdomen into the amniotic sac, a fluid filled area surrounding the baby. A small amount of fluid is withdrawn and sent to the laboratory for testing.

Just as you shed skin cells every day, so does your baby. This fluid contains some of your baby’s cells. Each cell contains the baby’s genetic information. The lab can look at the cells to determine if your baby has certain genetic conditions. Typically, an amniocentesis only takes a couple of minutes.

Who will perform the amniocentesis?
A maternal fetal medicine specialist will perform the procedure with assistance from a sonographer.

What does an amniocentesis test for?
Amniocentesis commonly tests for chromosome conditions, such as Down syndrome (Trisomy 21), Trisomy 18, Trisomy 13 and differences in the number of X or Y chromosomes. Amniocentesis can also detect open neural tube defects, such as spina bifida, if requested.

Your provider may request additional specific tests if a known genetic condition runs in a family (cystic fibrosis, muscular dystrophy or sickle cell disease) or if an abnormality is found through ultrasound (heart defect or skeletal abnormalities).

It is important to know that amniocentesis cannot detect all genetic conditions or birth defects. Because these conditions are all very different from one another, it’s not always possible to know how your baby’s health may be affected.

When will I get the results?
In most cases, you will get the results in 10 to 14 days, but it depends on the test.

How certain are amniocentesis results?
Amniocentesis is a diagnostic test, which means results are considered to be definitive for the conditions tested. In other words, this test will give you “yes” or “no” answers. Rarely, lab errors or uncertain results may occur.

What are the risks associated with amniocentesis?
Over 99 percent of the time, there are no serious complications. However, the test may increase the risk for some complications including leaking of amniotic fluid. There is also a small chance of miscarriage.

What can I expect after the procedure?
You may experience some brief discomfort such as cramping, pressure or pinching. This cramping may last for a few hours but should not last longer than 24 hours. Women usually return to their normal activities within 12 days following amniocentesis.

Chorionic Villus Sampling (CVS)

CVS is an optional procedure that can be performed between approximately 10 to 14 weeks of pregnancy. CVS involves collecting cells from part of the placenta called the chorionic villi. The cells collected contain genetic information that is usually identical to the baby.

There are two ways to perform CVS, through the cervix or through the mother’s abdomen, to remove and test cells from the placenta. The CVS typically only takes a few minutes to complete.

Who will perform the CVS?
A maternal fetal medicine specialist will perform the procedure with assistance from a sonographer.

What does CVS test for?
The most common conditions detected by CVS are chromosome conditions, such as Down syndrome (Trisomy 21), Trisomy 18, Trisomy 13 and differences in the number of X or Y chromosomes. Your provider may request additional specific tests if a known genetic condition runs in a family (cystic fibrosis, muscular dystrophy or sickle cell disease) or if an abnormality is found through ultrasound (heart defect or skeletal abnormalities).

It is important to know that CVS cannot detect all genetic conditions or birth defects. Because these conditions are all very different from one another, it’s not always possible to know how your baby’s health may be affected.

How certain are CVS results?
CVS is a diagnostic test which means results are considered to be definitive for the conditions tested. In other words, this test will give you “yes” or “no” answers. Rarely lab errors or uncertain results may occur. In a small number of cases the baby’s genetic information will be different than that of the placenta and further testing, such as amniocentesis, may be recommended to clarify uncertain CVS results.

When will I get the results?
In most cases, you will get the results in 10 to 14 days, but it depends on the test.

What can I expect after the procedure?
After CVS, most women return to their normal activities within 1 to 2 days. Discomfort may include a cramping sensation. Most women have no complications from having a CVS, however, there is a small chance for miscarriage.