What Is the NIPT Test?

Noninvasive Prenatal Testing for Genetic Conditions

Noninvasive prenatal testing (NIPT) is a screening test that can be performed early in your pregnancy. Here’s what you should know about what this test looks for, how it’s done, and how to interpret the results.

Pregnant couple meeting with doctor to review lab results

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What Is NIPT?

NIPT (also called prenatal cell-free DNA screening) is a screening test that estimates the risk that your baby will be born with a genetic abnormality, including Down syndrome.

NIPT analyzes fragments of the baby’s DNA found circulating in a pregnant person’s blood. DNA is usually located within cells. When cells break down, they release DNA into the bloodstream. This DNA is called cell-free DNA (cfDNA).

During pregnancy, the pregnant person’s blood will contain their own cell-free DNA and cell-free DNA from the placenta, the organ that develops during pregnancy and provides oxygen and nutrients to the growing fetus. Since the DNA from the placenta is usually identical to the baby’s DNA, it can be analyzed without any harm or risk to the baby.

What Conditions Does NIPT Look For?

NIPT screens for conditions caused by extra or missing chromosomes (aneuploidy). Chromosomes are the parts of cells that contain your DNA. Each cell normally has 23 pairs of chromosomes (46 total chromosomes). If one pair has an extra or missing chromosome, the development of the brain and body can be affected.

Chromosomal disorders may result in a nonviable pregnancy (one that will not result in a live birth) or a baby born with intellectual disabilities, differences in appearance, an inability to grow properly, or a shortened life expectancy.

Chromosomal abnormalities occur in approximately one in 150 live births, with the rate earlier in pregnancy being greater and often resulting in pregnancy loss.

NIPT screens for the three most common chromosomal aneuploidies:

NIPT can also detect sex chromosome disorders. The first 22 pairs of chromosomes are autosomes—common for both males and females. The 23rd pair is the sex chromosomes, and they come in two forms: X and Y. These chromosomes determine your biological sex.

Males have an X and a Y chromosome, while females have two X chromosomes. Sex chromosome disorders occur when extra or missing X or Y chromosomes are present.

NIPT tests for the following sex chromosome disorders:

NIPT will also reveal the baby's sex, so be sure to let your healthcare professional know if you want this information or prefer to be surprised on your delivery day.

Who Should Get NIPT?

Some laboratories offer additional testing for other conditions. Talk with your healthcare professional to determine which company they use for their NIPT and which specific conditions will be included in your results.

The American College of Obstetricians and Gynecologists previously recommended NIPT only for pregnant people who were considered of high risk based on their age, personal or medical history, or family history. However, the latest recommendations state that physicians should offer all pregnant patients NIPT, regardless of their risk.

While the risk of chromosomal abnormalities increases with a pregnant person’s age, these disorders can occur at any age. Other factors associated with an increased risk include:

  • Abnormal ultrasound findings
  • A chromosomal disorder present in either genetic parent of the baby
  • Previous pregnancy with a chromosomal abnormality

How Is the NIPT Performed?

NIPT requires a simple blood draw. A healthcare professional will obtain a blood sample from a vein in your arm using a needle. Blood is collected in a vial and sent to a laboratory to be analyzed.

There is no risk to your baby and only minimal risk to you. You may experience slight pain or bruising where the needle entered your arm.

NIPT can be performed right up until you deliver. The earliest you can get the test is after the first nine weeks of pregnancy.

Understanding the Results

NIPT is a screening test, which means it can only estimate the risk of having a particular disease; it cannot tell you for sure if your baby will be born with the condition.

While the test’s overall accuracy is high, the results may give a false positive (meaning it reports an increased risk when the condition is not present) or a false negative (meaning it reports a decreased risk when the condition is present).

Additionally, NIPT does not screen for all chromosomal or genetic conditions; therefore, a negative result does not rule out the possibility of your baby having another disorder.

If you receive a positive screening result (indicating an increased risk), you will need a diagnostic test to confirm if your baby has the condition. One of two diagnostic tests may be performed: an amniocentesis or chorionic villus sampling.

An amniocentesis involves removing a small amount of amniotic fluid (the fluid surrounding your baby inside the uterus) for analysis. Chorionic villus sampling takes a tissue sample of the placenta. Unlike NIPT, these tests are considered invasive, and there is a slight chance of miscarriage.

Sometimes, NIPT results will come back as “no result reported.” This most commonly occurs when the amount of cell-free DNA from the pregnancy is too low.

The proportion of cell-free DNA from the pregnancy compared to the cell-free DNA in your blood is called the fetal fraction. NIPT requires a fetal fraction of at least 4% to provide accurate results.

The fetal fraction may be lower in people who have higher body weights or if the testing is performed too early in the pregnancy. Other factors may impact the ability of NIPT to provide a result. Your healthcare professional will discuss the next steps with you based on your specific situation.

Options include:

  • Repeating the NIPT
  • Choosing a different screening test
  • Undergoing diagnostic testing
  • Declining further testing

A Word From Verywell

Pregnancy can come with seemingly endless testing and frequent visits to the doctor. While it's ultimately up to you how much testing you'd like to complete, understanding the purpose and background of available prenatal screenings will help you make an informed choice that's best for you and your baby.

While it can be hard not to worry after receiving unfavorable results from the NIPT, it's important to keep in mind that this is not a diagnostic test. You may not know the full scope of your baby's health until additional tests are completed (or sometimes until the birth).

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Article Sources
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