A NIPT result may contain a reassuring phrase, a worrying flag, or no answer at all. Understanding which of those you have is the first step. A “high chance” result is not a diagnosis, and a “low chance” result does not mean every genetic condition has been excluded.
This guide helps you read the report and prepare questions for your maternity or genetics team. The examples are fictional and are not estimates of your pregnancy’s risk.
What NIPT actually measures
Noninvasive prenatal testing, also called cell-free DNA screening or NIPS, analyses DNA fragments circulating in the pregnant person’s blood. Most come from the pregnant person; the pregnancy-related component mainly comes from the placenta. Placental DNA usually reflects the fetus, but the two are not always identical. This is one reason a screening result can disagree with diagnostic testing. MedlinePlus explains the biology.
The main established targets are trisomy 21, trisomy 18 and trisomy 13. Tests can offer additional targets, but evidence and performance differ by condition. Never assume that a headline accuracy figure applies to everything listed on a panel.
Read the report in this order
- Identify the target. Which chromosome or condition does the result concern?
- Read the result category. Is it lower chance, increased chance, or nonreportable?
- Check the context. Does the report correctly describe the pregnancy, including whether it is a twin pregnancy?
- Locate the limitations. Look for excluded conditions and any sample-quality or fetal-fraction comment.
- Agree on follow-up. Ask who will explain the result and whether further assessment is appropriate.
| Result | Meaning | Useful next question |
|---|---|---|
| Lower chance / negative | The screened condition is less likely; risk is not zero. | Does anything in my history or ultrasound need separate assessment? |
| Increased chance / positive | The screen suggests increased probability; it has not established a diagnosis. | What counselling and diagnostic options can clarify this? |
| No result / nonreportable | The laboratory could not provide a usable screening answer. | Why did this happen, and what follow-up fits my pregnancy? |
For the broader distinction, see prenatal screening versus diagnostic testing.
Example 1: why “99% sensitive” does not mean “99% certain”
Fictional teaching example. Imagine a screening test—not a real NIPT product—used in 10,000 pregnancies. Suppose 100 have the target condition. For this calculation only, assume 99% sensitivity and 99% specificity.
| Group | Total | Positive screens |
|---|---|---|
| Pregnancies with the target condition | 100 | 99 true positives |
| Pregnancies without the target condition | 9,900 | 99 false positives |
| All positive screens | — | 198 |
Among the 198 positive screens, 99 are true positives: the positive predictive value is 50%, despite 99% sensitivity. Sensitivity asks how many affected pregnancies the test detects. Positive predictive value asks how many positive results are truly affected. The starting frequency of the condition changes that second answer.
Do not use this example to interpret your own report. Ask for the condition-specific positive predictive value and how it was estimated. “Accuracy” without a named measure, population and target condition is not enough information.
What happens after an increased-chance result?
The maternity team can arrange genetic counselling and discuss diagnostic testing, which may involve chorionic villus sampling or amniocentesis. The appropriate procedure and laboratory analysis depend on the finding and the pregnancy. MedlinePlus describes why additional testing is needed to confirm or exclude a diagnosis. Major irreversible pregnancy decisions should not rest on a screening result alone.
Bring the full report. A useful question is: “Which test would resolve this particular uncertainty?” Repeating a screen is not equivalent to diagnostic confirmation.
Example 2: a no-call result is not a negative result
Fictional teaching example. A report says that there was insufficient pregnancy-related DNA for analysis. The family assumes this means nothing abnormal was found. In fact, the test did not produce an interpretable answer.
Nonreportable results have several possible causes, including early sampling and low fetal fraction. They can also be associated with increased risk of a chromosome condition. Follow-up should be discussed with the maternity team; counselling, ultrasound and diagnostic testing may be appropriate. Whether a repeat sample is useful depends on circumstances and timing. SMFM explains the follow-up issues.
Example 3: a reassuring screen and a later ultrasound finding
Fictional teaching example. A low-chance result for the common trisomies is followed by an ultrasound finding. The earlier screen does not make that finding irrelevant: the two assessments answer different questions.
NIPT is not a complete examination of fetal structure or every gene. The clinician should review the ultrasound and discuss whether additional assessment could explain it. Keeping the actual screening report available helps avoid the misleading shorthand “all genetic tests were normal.”
Are more screening targets always better?
No. In its 2025 updated guidance, SMFM recommends making screening for sex-chromosome differences an opt-in choice after counselling and recommends against routine population screening for microdeletions. A longer test menu is not a substitute for evidence about benefit, false positives and follow-up. See SMFM Consult Series 74. These are US professional recommendations; local services and guidance may differ.
Questions worth taking to the appointment
- Which findings were actually screened for, and which were not?
- What does this result mean for this condition in my pregnancy?
- Would further testing be screening or diagnosis?
- What uncertainty would remain after that test?
- When will results be available, and who will discuss them with me?
Our genetic counselling guide and genetics-care finder can help you prepare for professional advice. The decision to accept or decline testing should be informed and voluntary.