Types of Genetic Screening: What it Tests For and Who Should Get It

Types of Genetic Screening

There are a few different types of genetic screening available to expecting parents that can be performed during pregnancy:

Carrier Screening

This type of genetic screening determines if there is an increased risk of expecting parents carrying a genetic condition that could be passed on to their unborn child, according to The March of Dimes. In some cases, parents do not have the condition themselves but they do carry the gene associated with the condition and this could pose a risk to their child. This test is conducted by testing the parent’s blood or saliva. It’s important to note that this type only tells you if you or the baby’s biological father have a gene associated with a genetic condition–it does not identify if your baby actually has the condition.

Prenatal Genetic Screening

Prenatal genetic screening focuses on the unborn child and looks for indications that they’re at risk for a genetic disorder. First trimester screening, second trimester screening, and prenatal cell-free DNA testing are all types of prenatal genetic screening options.

• First trimester screening

  This is done between the 10th and 13th week of pregnancy. This screening includes an ultrasound and blood tests for the expecting parent. Through the blood tests, providers are looking for abnormal levels of pregnancy-associated plasma protein-A and human chorionic gonadotropin, which could indicate the fetus is at risk for a genetic condition, according to Stanford Children’s Health.

• Screening ultrasound

The ultrasound performed during the first trimester tests for fetal nuchal translucency– the thickening of skin on the back of the neck–or increased fluid, which can be signs of a chromosomal abnormality, such as Down Syndrome.

• Second trimester screening

  As the name suggests, these screenings are performed later in the pregnancy, between weeks 15 and 20. They include more comprehensive blood tests that look for abnormal levels of three different hormones —hCG, Estriol, and Inhibi—as well as alpha-fetoprotein. Your doctor can help you decide if these blood tests belong on your second trimester checklist.

• Prenatal cell-free DNA testing

  This is a blood test that can be done in the first trimester. It looks at both the mother’s DNA and DNA from the pregnancy that is present in the mother’s blood. This test is most frequently used to check for trisomy 21, 18, and 13. If there is more DNA from these chromosomes than deemed within the range of normal, this could indicate the baby is at risk for a genetic condition.

One key note about types of genetic screenings: none of these screening procedures are considered diagnostic. That means they can’t tell you for sure if your child has or doesn’t have a certain condition. Instead, they provide parents with information about the risk of the unborn child having a genetic condition. For this reason, it is important for parents to understand that a positive or negative result on any of these tests doesn’t determine if your child has a genetic condition. Instead, these screenings offer a look at the likelihood of a genetic condition and indicate if further testing might be appropriate. If your provider is concerned about the results, they may suggest pursuing genetic testing. Genetic testing include amniocentesis (to get a sample of amniotic fluid) or chorionic villus sampling (to get a small sample of the placenta). These tests are considered diagnostic and they are nearly 100% accurate. Many insurance plans will cover genetic testing if your prenatal care provider has indicated it is an appropriate choice for you and your baby.

Genetic Testing in Pregnancy

Genetic screening isn’t for everyone. Generally, it is recommended that parents with a family history of genetic conditions or birth defects strongly consider prenatal genetic screening. Your doctor may also recommend genetic testing if you are over the age of 35, since the likelihood of a genetic disease increases with age. Carrier genetic screening and prenatal genetic screening are low risk. The biggest consideration is how the results will affect your emotional well-being and mental health and what the results will mean for the future of your pregnancy. Since these tests aren’t 100% accurate, having genetic screening may cause additional anxiety for parents until they are able to pursue further testing. Others may find that their results provide them with relief from their anxiety and a chance to make plans for the future. Personal beliefs can impact your choice as well. It’s a good idea to consider ahead of time how you and your partner would feel if the results show your baby has a high risk of a genetic condition.

During my first pregnancy, we met with our doctor and were referred to a genetic counselor to discuss risks based on a birth defect in my family history. The counselor was able to show us what kind of risks our family history might come with and ease our worries about our baby. That information alone was enough to help us decide if we wanted to pursue genetic testing. For expecting parents who are on the fence about genetic screening, know that this is a highly individual decision and either choice can be appropriate depending on the circumstances.