Understanding Genetic Screening in Pregnancy: Tests, Choices, and Support

Highlights

• Genetic screening (prenatal screening) tests estimate the chances that your baby could have a genetic or chromosomal condition — they are available to anyone who is pregnant.
• You have the right to choose whether or not to undergo a prenatal screening test.
• Screening tests include the combined first trimester screening test, maternal serum screening, and the non-invasive prenatal test (NIPT).
• If your screening test shows that your baby has a high chance of having a genetic condition, a genetic counsellor can help you decide on further testing, which may include chorionic villus sampling (CVS) or amniocentesis.

In This Article

• Overview of Genetic Screening in Pregnancy
• Types of Genetic Screening Tests
• Combined First Trimester Screening
• Second Trimester Maternal Serum Screening
• Non-Invasive Prenatal Test (NIPT)
• Making the Right Choice
• What to Expect After Screening
• Costs of Genetic Screening
• Genetic vs. Carrier Screening
• Tools And Assistance

Overview of Genetic Screening in Pregnancy

Genetic screening, or prenatal screening, is available to anyone who is pregnant. These tests estimate the likelihood that your baby has a genetic, chromosomal, or physical condition.

There are different types of tests available. They vary in how accurate they are and what information they can provide. No single test checks for all conditions, which is why multiple screenings might be considered.

It’s essential to remember that the majority of babies are born healthy, regardless of genetic screening results. These tests are just one way to help assess the likelihood of certain conditions.

Types of Genetic Screening Tests

There are several types of genetic screening tests, each with different methods and levels of accuracy. They are commonly offered during pregnancy, with some being more invasive than others. Below are the most commonly used screening tests:

Combined First Trimester Screening

The combined first trimester screening (CFTS) involves a combination of a maternal blood test and an ultrasound scan to assess the chances of your baby having certain genetic conditions, including:

• Down syndrome (trisomy 21)
• Edwards syndrome (trisomy 18)
• Patau syndrome (trisomy 13)

This test measures factors such as:

• The levels of certain proteins in the mother’s blood
• The thickness of the fluid behind the baby’s neck (nuchal translucency)
• The presence or absence of the baby’s nasal bone
• The mother’s age and weight
• How far along the pregnancy is

This test can be done between 9 weeks and 13 weeks and 6 days of pregnancy.

Second Trimester Maternal Serum Screening

Second trimester maternal serum screening involves a blood test to calculate the likelihood of the baby having:

• Down syndrome (trisomy 21)
• Edwards syndrome (trisomy 18)
• Neural tube defects (e.g., spina bifida)

This test evaluates factors such as:

• Blood test results
• The mother’s age and weight
• Pregnancy age

This test is typically performed between 15 and 17 weeks of pregnancy but can be done up to 20 weeks.

Non-Invasive Prenatal Test (NIPT)

The non-invasive prenatal test (NIPT) is one of the most accurate screening tests for certain genetic conditions. It uses a small sample of the mother’s blood, which contains fragments of the baby’s DNA. The test is performed after 10 weeks of pregnancy.

NIPT estimates the chances that your baby may have:

• Down syndrome
• Edwards syndrome
• Patau syndrome
• Sex chromosome conditions
• Microdeletion syndromes

This test is also capable of identifying the baby’s sex.

NIPT is considered the most accurate screening test for detecting Down syndrome. It is still a screening test and not a diagnostic one. Speak with your healthcare provider about accessing NIPT if you’re interested.

Making the Right Choice

Deciding whether or not to undergo prenatal screening can be difficult. It is a personal decision that may come with a lot of emotional weight.

Before making a decision, it’s important to discuss your options with a healthcare professional, such as your doctor or midwife. They can explain the advantages and disadvantages of each test, and help you understand what further tests may be required if a screening shows a high risk.

During these discussions, your healthcare provider will explain the evidence for each test and its potential outcomes. This process is called “shared decision making.” Ultimately, it’s your choice.

What to Expect After Screening

If your prenatal screening test shows that your baby has a higher chance of having a genetic condition, you may be offered genetic counselling. A genetic counsellor will provide more information and support to help you understand the results.

They will also help you consider your next steps, which may include further diagnostic tests such as chorionic villus sampling (CVS) or amniocentesis.

These diagnostic tests provide a definitive result. You do not need to undergo them if you choose not to. However, your healthcare provider can help you understand the implications of your choices.

Costs of Genetic Screening

The cost of prenatal screening tests depends on several factors:

• Whether you are a public or private patient
• The type of test being performed
• The healthcare provider’s recommendations

Some tests may be partially reimbursed, but many—especially the NIPT—may require out-of-pocket payment.

Genetic vs. Carrier Screening

Genetic (prenatal) screening is done during pregnancy to estimate the chances that your baby could have a genetic condition. In contrast, carrier screening checks whether you or your partner carry genes for inherited conditions, even if you don’t show symptoms.

Carrier screening is usually done before pregnancy but can also be done early in pregnancy. Both types of screening offer valuable information for making informed decisions.

Tools And Assistance

After receiving the results of a prenatal screening test, it’s completely normal to feel anxious, uncertain, or overwhelmed. Support is available at every step of the journey, and you don’t have to go through it alone.

Who you can talk to:

• Your doctor or midwife can help explain your test results and guide you through possible next steps based on your individual situation.
• A genetic counsellor can provide detailed information about what the results mean, outline the risks, explain diagnostic testing options, and support you in making decisions that align with your values and preferences.

Additional support options:

• Mental health professionals such as psychologists or counsellors can assist with emotional well-being, especially if you’re feeling stressed or overwhelmed.
• Peer support groups or parent communities can connect you with others who have gone through similar experiences, offering a sense of solidarity and shared understanding.
• Family and friends can also be a valuable source of emotional and practical support during this time.

Reaching out for support is a positive step. You deserve clear information and compassionate guidance while making decisions about your pregnancy and your family.

Need more information?

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