Prenatal genetic counseling and testing

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?

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.

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.

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.

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.

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.

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) 
• Hemoglobinopathy 
• Tay-sachs 

Expanded panels testing for additional conditions may be indicated based on your ethnicity or family history.

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.

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.

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

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.

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

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.

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.

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.

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.

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.

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

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.