Pregnancy
NIPT Test in Pregnancy: What It Screens For, Accuracy and What Results Mean
NIPT (noninvasive prenatal testing), also called cell-free DNA screening, is a blood test you can have from about 10 weeks of pregnancy. It screens for Down syndrome (trisomy 21), trisomy 18, trisomy 13 and, if you want, sex chromosome differences. It's the most accurate screening test for these conditions, but it isn't a diagnosis. A high-risk result needs a diagnostic test to confirm it.
For most people, the test itself is the easy part: one regular blood draw, often at the same visit as your other first-trimester labs. The waiting and the results are where the questions come in. Here's what to expect from start to finish.
How it works
During pregnancy, small fragments of DNA from the placenta float in your bloodstream. That's the "cell-free DNA." NIPT counts these fragments from a standard draw from your arm. If there's more or less DNA from a particular chromosome than expected, the lab flags a higher chance of a chromosome condition.
The placenta usually has the same genetic makeup as the baby, so NIPT is a very good stand-in for testing the baby directly. And because it's just your blood, there's no miscarriage risk.
The timeline, step by step
Before the draw (around 10 to 13 weeks). Your provider offers it, ideally with a short conversation about what it does and doesn't check. Decide now whether you want to learn the baby's likely sex, and tell them. If you want it to be a surprise, ask that it be left off your portal too, since results can post before anyone calls you.
The draw. A few tubes of blood. No fasting, no special prep.
The wait. Results often take about one to two weeks, depending on the lab. Many people say this is the hardest stretch. Ask how you'll get results (call, portal, or at your next visit) so you're not refreshing an app at midnight.
The result. Usually one of three: low risk, high risk, or no-call. Each is explained below.
What NIPT screens for
Standard panels look for:
- Trisomy 21 (Down syndrome)
- Trisomy 18 (Edwards syndrome)
- Trisomy 13 (Patau syndrome)
- Sex chromosome conditions, such as Turner syndrome (one X) or extra X or Y chromosomes, plus the likely sex of the baby
Some labs offer add-ons for small missing pieces of chromosomes (microdeletions) or rarer trisomies. ACOG doesn't recommend routine microdeletion screening, because those tests are less well studied and give more false alarms. Ask whether an expanded panel makes sense for you.
What NIPT doesn't check
- Neural tube defects like spina bifida. These are screened with an AFP blood test in the second trimester and with the anatomy ultrasound.
- Most structural differences, such as heart defects. The 20-week anatomy scan looks for these.
- Single-gene conditions like cystic fibrosis. Carrier screening of the parents covers these.
How accurate is it?
NIPT detects the large majority of pregnancies with Down syndrome and has a very low false-positive rate, better than older blood-test screens. It's somewhat less accurate for trisomies 13 and 18 and for sex chromosome conditions.
The number that matters most is the positive predictive value: if your result says "high risk," what's the actual chance the baby has the condition? That depends on how common the condition is at your age. For a younger patient, a high-risk result is more likely to be a false positive than for an older one. Your report or a genetic counselor can give you your specific number. Ask for it.
Why NIPT can be wrong
- Confined placental mosaicism: the placenta has a chromosome change the baby doesn't
- A vanishing twin: DNA from a twin that stopped developing early
- Maternal factors: rarely, a chromosome change or medical condition in the pregnant person
- Low fetal fraction: too little placental DNA in the sample
If you get a "no-call" result
Sometimes the lab can't give a result, usually because there wasn't enough placental DNA. It's more common early in pregnancy and in people with higher body weight. A no-call is sometimes linked to a higher chance of a chromosome condition, so your provider will usually suggest a repeat draw, an ultrasound, genetic counseling or diagnostic testing. It's frustrating, and it's not a diagnosis.
If you get a high-risk result
Take a breath. High risk means "look further," not "your baby has this." Typical next steps:
- Genetic counseling to explain your specific result and options. Many hospital systems can get you in within days; ask for the soonest slot.
- A detailed ultrasound, sometimes with a maternal-fetal medicine specialist
- Diagnostic testing, which looks at the baby's or placenta's cells directly:
| Test | When | What it samples | Notes |
|---|---|---|---|
| CVS (chorionic villus sampling) | About 10–13 weeks | Small sample of placenta | Earlier answer; small risk of miscarriage |
| Amniocentesis | From about 15 weeks | Amniotic fluid | Tests the baby's cells; small risk of miscarriage |
ACOG advises against ending or changing the course of a pregnancy based on a cell-free DNA result alone, without diagnostic confirmation.
NIPT vs. first-trimester screening
| Cell-free DNA (NIPT) | First-trimester screen | |
|---|---|---|
| Timing | From about 10 weeks | About 11–14 weeks |
| How | Blood draw | Nuchal translucency ultrasound plus blood tests |
| Detection of Down syndrome | Highest of the screening tests | Good, but lower than NIPT |
| False positives | Very low | Higher |
| Also gives | Likely sex of the baby | Early look at the baby's anatomy |
Some people do both. The nuchal translucency ultrasound can spot some structural problems NIPT can't.
Twins
Cell-free DNA screening can be done with twins, but it's less studied than with one baby and may be less precise, especially for telling which twin is affected. See twin pregnancy for more on extra monitoring.
Is NIPT covered by insurance in New York?
Coverage depends on your plan. Many insurers now cover cell-free DNA screening for everyone who's pregnant, while some still limit it by age or risk. Before the draw, ask the office or the lab for a cost estimate and whether prior authorization is needed. Some labs will text or email you a price estimate before they run the sample. If you have NY Medicaid, ask your provider which prenatal genetic tests your plan covers.
Should I get NIPT?
Prenatal genetic screening is always optional. Some people want as much information as possible. Others skip it, or only want results that would change their care. Questions worth sitting with:
- Would the result change how I manage the pregnancy or prepare for birth?
- Would I want diagnostic testing if the screen came back high risk?
- Do I want to know the sex early?
A genetic counselor can help you think it through without pressure.
When to call your provider
Contact your provider or ask for genetic counseling if:
- You get a high-risk or no-call result
- Your result doesn't match what was seen on ultrasound
- You have a family history of a genetic condition, or a previous pregnancy with a chromosome condition
- You're unsure whether you want screening or diagnostic testing
To find an OB/GYN or MFM specialist who offers genetic counseling, browse MFM specialists on Long Island or search the directory.
Frequently asked questions
When can you do the NIPT test?
NIPT, also called cell-free DNA screening, can be done any time from about 10 weeks of pregnancy. Most people have it between 10 and 13 weeks so results come back early.
Is NIPT a diagnosis?
No. It's a screening test that tells you whether the chance of a condition is high or low. A high-risk result should be confirmed with a diagnostic test such as CVS or amniocentesis before making any decisions.
Can NIPT tell the baby's sex?
Yes, most NIPT panels can report the sex chromosomes, so you can learn the likely sex early if you want to. You can also ask not to be told.
Is NIPT only for people over 35?
No. ACOG recommends that all pregnant people be offered screening for chromosomal conditions, including cell-free DNA, regardless of age.
Sources
- ACOG — Screening for Fetal Chromosomal Abnormalities (Practice Bulletin 226)
- ACOG — Prenatal Genetic Screening Tests FAQ
- MedlinePlus — Noninvasive Prenatal Testing
- NIH National Human Genome Research Institute — Prenatal Genetic Testing
This article is for general education and is not medical advice. It does not replace an evaluation by a licensed clinician who knows your history. If you think you have a medical emergency, call 911.