Prenatal Testing: Do You Know the Benefits and Limits?

Find out what it can offer you

Prenatal Testing: Do You Know the Benefits and Limits?

Noninvasive prenatal testing (NIPT) can offer important clues about your developing baby’s health. In some cases, the test may help you make informed healthcare decisions for your child, both in utero and after birth.

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But interpreting NIPT results is tricky. There are some things the test can tell you — and many things it can’t.

Certified genetic counselor Marissa Coleridge explains who might have the testing, how the test works and what the results may mean for you.

Who should have noninvasive prenatal testing?

NIPT is a blood screening your doctor may offer any time after 10 weeks gestation during your pregnancy. Most often, your doctor will recommend the testing if you are at higher risk of carrying a child with a chromosomal abnormality, Ms. Coleridge says.

Risk factors include:

  • Being age 35 or older.
  • Having a prior pregnancy with a chromosomal condition.
  • Having abnormal test results from other tests or screening.

You may also opt for the testing if you don’t have risk factors, she says.

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What can the results tell you?

“The tricky part of NIPT is that it can’t screen for every genetic condition. It’s very targeted,” Ms. Coleridge says.

NIPT works by analyzing cell-free DNA which is made up of maternal, fetal and placental DNA in your blood. The test can tell you if you are at higher risk of having a baby with Down syndrome, Trisomy 18 or Trisomy 13. These are all genetic conditions that can cause developmental delays and physical or mental defects.

The testing also looks at the number of your baby’s sex chromosomes, which can tell you whether you’re having a boy or a girl. If it finds extra or missing sex chromosomes, that also may signal a genetic condition.

While the test is a safe way to screen for the three chromosomal conditions, it can’t tell you for sure whether your child will have one of them.

“We never recommend making life-changing decisions based on NIPT results because it’s a non-diagnostic test,” Ms. Coleridge cautions. “There is a false negative rate, and a false positive rate, albeit less than 1 percent.”

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Your results are positive, now what?

If your NIPT results are positive (suggesting an abnormality), your doctor may encourage you to meet with a genetic counselor.

A counselor can help you better understand your results. He or she will discuss options for follow up, including diagnostic tests and additional imaging.

Knowing more about your baby’s health can help guide your management while you’re pregnant and better prepare for your baby’s care during and after delivery.

Keeping results in perspective

While receiving positive NIPT results is often unsettling, it’s important to keep the results in perspective.

“NIPT test results aren’t absolute,” says Ms. Coleridge. “There are some things that can throw the test off, which is why meeting with a genetic counselor and talking with your healthcare team to discuss results is very important.”

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