What is the difference between carrier screening and prenatal cfDNA screening?

Starting a family is a personal journey, but it’s also a medical one, filled with many decisions and considerations. Medical experts recommend that healthcare providers offer two kinds of genetic screenings to people who are growing their family: a carrier screen and a cell-free DNA (cfDNA) screen.

Screening tests are different than diagnostic tests. Screening tests do not give definitive answers. Screening tests provide information about the chances of a genetic change posing a health concern. Knowing what each test is can help you make choices that are right for you and your family. Let’s break down what each of these screenings involves and how they differ.

Carrier screening

What is it? 

• Carrier screening is a genetic test that helps determine if you and/or your partner carry a gene for a genetic disorder that could be passed on to your baby.

When is it done?

• Ideally, before pregnancy or early in pregnancy.

What can it test for?

• Common genetic conditions such as cystic fibrosis, sickle cell disease, Tay-Sachs disease, and many others.

How is it done?

• A simple blood or saliva test.

Why is it important?

• Knowing if you are a carrier can help you understand the risk of passing a genetic condition to your child.
• It allows you to make informed decisions about your pregnancy and future family planning.

Prenatal cfDNA screening

What is it? 

• During pregnancy, small pieces of the baby’s DNA from the placenta enter the blood stream of the pregnant person. Prenatal cfDNA screening, also known as non-invasive prenatal testing (NIPT), analyzes these small DNA fragments circulating in your blood to assess the risks for the baby and the pregnancy.

When is it done?

• As early as eight weeks into your pregnancy.

What does it test for?

• Chromosomal abnormalities such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13).
• Some tests can also predict the baby’s sex, and the chances for other more rare chromosome conditions.

How is it done?

• A blood sample from the pregnant person.

Why is it important?

• It provides early information about your baby’s risk for certain chromosome conditions.
• It is non-invasive and poses no risk to the pregnancy.

Some key differences

• Purpose: Carrier screening is about understanding your genetic makeup and the risk of passing on genetic disorders. Many people are carriers of inherited conditions and don’t know it. Some couples only find out about this when they perform carrier screening or after they have a baby that is affected by the condition. Prenatal cfDNA screening focuses on detecting the risk of chromosomal abnormalities that usually happen by chance in the developing baby.
• Timing: Carrier screening is best done before or early in pregnancy, while prenatal cfDNA screening is done during pregnancy.
• Method: Carrier screening uses blood or saliva samples from the parents or donors, whereas prenatal cfDNA screening uses a blood sample from the pregnant person.

Making the choice

Deciding which screenings to undergo can feel overwhelming, but here are a few tips to help:

• Consult with your healthcare provider: They can provide personalized advice based on your medical history and family background.
• Consider your peace of mind: Knowing more about your baby’s health can help you feel more prepared and less anxious.
• Think about the future: Understanding potential risks can help you make informed decisions about your pregnancy and family planning.

Final thoughts

Both carrier screening and prenatal cfDNA screening offer valuable insights into your baby’s health. By understanding the differences and benefits of each, you can make informed choices that are best for you and your family. Remember, your healthcare provider is your best resource for guidance and support throughout this journey.