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PubMed This is a summary of 27 peer-reviewed journal articles Updated
Obstetrics

Is a Positive NIPT for Down Syndrome Always Accurate?

At a Glance

A positive NIPT result for Down syndrome indicates a higher risk but is not a definitive diagnosis. False positives can occur because the test analyzes placental DNA, which doesn't always perfectly match the baby's DNA. Further diagnostic testing is required to know for sure.

Receiving a “high risk” or positive result on a Non-Invasive Prenatal Test (NIPT) for Down syndrome can be terrifying, but the most important thing to know is this: a positive NIPT does not mean your baby definitely has Down syndrome. NIPT is highly sensitive and very good at spotting potential issues, but it is a screening test, not a diagnostic test [1][2]. This means it can only tell you if your pregnancy is at a higher risk, but it cannot diagnose the condition with absolute certainty [3]. Medical guidelines clearly state that irreversible clinical decisions should never be made based solely on an NIPT result [4].

Understanding Positive Predictive Value (PPV)

When your doctor says your result is “high risk,” you need to know what the actual mathematical percentage is that your baby has the condition. In medicine, this is called the Positive Predictive Value (PPV). PPV answers the question: Out of all the people who get a positive test, how many actually have the condition? On your lab paperwork, you might see NIPT referred to as cell-free DNA (cfDNA) screening [5].

Your specific PPV is heavily based on your age and baseline risk [6][7]. Because Down syndrome occurs more frequently as maternal age increases, the test’s positive results are much more accurate for older mothers [8][9].

  • For older expectant mothers (often defined as >35 or >40 years), the PPV for Down syndrome frequently exceeds 85% to 90% [10][11].
  • For younger expectant mothers (such as women in their 20s or early 30s), the chance of a false positive is much higher because the baseline risk is lower [6]. Depending on your exact age, the PPV could be around 50% or even lower—meaning the result is essentially a coin flip between a true positive and a false positive.

What Causes a False Positive?

You might wonder how a DNA test could be wrong. The answer lies in where the DNA comes from. NIPT analyzes cell-free DNA circulating in the mother’s blood, which actually originates from the placenta, not directly from the fetus [5][12].

Common causes of false positives include:

  • Confined Placental Mosaicism (CPM): Sometimes, a genetic abnormality occurs only in the placenta while the fetus remains genetically typical [12][13]. Because the NIPT analyzes placental DNA, it can flag the pregnancy as high risk even if the baby does not have Down syndrome [14].
  • Vanishing Twin: If a twin pregnancy started but one embryo was lost early on (a “vanishing twin”), the DNA from the lost twin can remain in your bloodstream for several weeks [15][16]. If that lost twin had a chromosomal difference, the NIPT might pick up their DNA, leading to a false positive [17].
  • Maternal Factors: Rarely, harmless genetic variations in the mother’s own cells or other rare maternal health conditions can alter the test results [13][18].

Next Steps: Counseling and Ultrasound

You do not have to figure out your next steps alone, nor do you have to rush immediately into invasive testing. Standard medical next steps include:

  • Genetic Counseling: Meeting with a Genetic Counselor or a Maternal-Fetal Medicine (MFM) specialist is highly recommended [19][20]. They can calculate your exact personal PPV and help you weigh your options.
  • Detailed Ultrasound: An ultrasound (such as a Nuchal Translucency scan or an early anatomy scan) provides critical context [21]. Doctors will look for “soft markers” or structural signs associated with Down syndrome, which can help clarify whether the NIPT result is likely a true positive [22].

Next Steps: Diagnostic Testing

To know for certain whether your baby has Down syndrome, a diagnostic test is required. Both primary options are highly accurate, but because they are invasive procedures, they carry a very small risk of miscarriage (typically estimated at a fraction of a percent) [23]. You and your doctor should weigh this small risk against your need for a definitive answer.

  • Chorionic Villus Sampling (CVS): Usually performed in the first trimester (typically between 10 and 13 weeks of pregnancy), this test takes a tiny sample of the placenta [24]. It allows for the earliest possible diagnosis [25]. However, because it tests the placenta (just like the NIPT), there is a very small chance that Confined Placental Mosaicism could still cause confusing results [26].
  • Amniocentesis: Usually performed in the second trimester (typically after 15 weeks of pregnancy), this test analyzes the amniotic fluid, which contains cells directly from the baby [24]. Amniocentesis is considered the definitive “gold standard” follow-up, especially if doctors suspect placental mosaicism [27][14].

Common questions in this guide

What does a high-risk NIPT result for Down syndrome mean?
A high-risk NIPT means your pregnancy has an increased chance of Down syndrome, but it is a screening result, not a diagnosis. You will need follow-up diagnostic testing to know for sure.
Can an NIPT test for Down syndrome be wrong?
Yes, false positives can happen because the test analyzes DNA from the placenta, not directly from the baby. Harmless genetic variations in the placenta, such as confined placental mosaicism, or DNA from a vanishing twin can cause an inaccurate high-risk result.
Does my age affect the accuracy of my NIPT result?
Yes, your age heavily impacts the test's Positive Predictive Value (PPV). Because Down syndrome occurs more frequently as maternal age increases, a positive NIPT is much more likely to be accurate for older mothers compared to younger mothers.
Should I get CVS or amniocentesis after a positive NIPT?
CVS can be performed earlier in pregnancy but tests the placenta, which can occasionally share the same inaccuracies as the NIPT. Amniocentesis is performed later but tests amniotic fluid directly from the baby, making it the definitive standard for diagnosis.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my exact age and the fetal fraction on my lab report, what is my personal Positive Predictive Value (PPV) for this result?
  2. 2.Are there any 'soft markers' or structural signs visible on my ultrasound that give us more information about the likelihood of a true positive?
  3. 3.Can you refer me to a Genetic Counselor or Maternal-Fetal Medicine (MFM) specialist to help me review my options?
  4. 4.What are the exact risks of miscarriage for CVS versus amniocentesis at this specific clinic or hospital?
  5. 5.If I choose to wait for an amniocentesis instead of getting a CVS now, how will that affect my timeline and options for the remainder of my pregnancy?

Questions For You

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References

References (27)
  1. 1

    Non-Invasive Prenatal Testing (NIPT): A Paradigm Shift in Prenatal Care.

    Garg RK, Kumar Y, Niwas R, Singh J

    International journal of preventive medicine 2025; (16()):86 doi:10.4103/ijpvm.ijpvm_266_25.

    PMID: 41624918
  2. 2

    Confined placental mosaicism and its impact on confirmation of NIPT results.

    Mardy A, Wapner RJ

    American journal of medical genetics. Part C, Seminars in medical genetics 2016; (172(2)):118-22 doi:10.1002/ajmg.c.31505.

    PMID: 27184347
  3. 3

    The Impact of Chromosomal Mosaicisms on Prenatal Diagnosis and Genetic Counseling-A Narrative Review.

    Militaru MS, Babliuc IM, Bloaje-Florică VL, et al.

    Journal of personalized medicine 2024; (14(7)) doi:10.3390/jpm14070774.

    PMID: 39064028
  4. 4

    Analysis of 17,428 pregnant women undergoing non-invasive prenatal testing for fetal chromosome in Northeast China.

    Dai R, Yu Y, Zhang H, et al.

    Medicine 2021; (100(6)):e24740 doi:10.1097/MD.0000000000024740.

    PMID: 33578623
  5. 5

    False Negative NIPT Results: Risk Figures for Chromosomes 13, 18 and 21 Based on Chorionic Villi Results in 5967 Cases and Literature Review.

    Van Opstal D, Srebniak MI, Polak J, et al.

    PloS one 2016; (11(1)):e0146794 doi:10.1371/journal.pone.0146794.

    PMID: 26771677
  6. 6

    New screen on the block: non-invasive prenatal testing for fetal chromosomal abnormalities.

    Filoche S, Lawton B, Beard A, et al.

    Journal of primary health care 2017; (9(4)):248-253 doi:10.1071/HC16055.

    PMID: 29530134
  7. 7

    Integrating NIPT and ultrasound for detecting fetal aneuploidies and abnormalities.

    Andonotopo W, Bachnas MA, Pribadi A, et al.

    Journal of perinatal medicine 2025; (53(7)):789-802 doi:10.1515/jpm-2025-0005.

    PMID: 40441708
  8. 8

    Non-invasive prenatal testing for the diagnosis of congenital abnormalities: Insights from a large multicenter study in southern China.

    Cai M, Lin N, Chen X, et al.

    Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologica 2023; (56()):e12506 doi:10.1590/1414-431X2023e12506.

    PMID: 37377305
  9. 9

    Performance analysis of non-invasive prenatal testing for trisomy 13, 18, and 21: A large-scale retrospective study (2018-2021).

    Lu YS, Chen YY, Ding SY, et al.

    Heliyon 2024; (10(13)):e33437 doi:10.1016/j.heliyon.2024.e33437.

    PMID: 39040373
  10. 10

    Effect of maternal age on foetal chromosomal defects: an investigation based on non-invasive prenatal testing.

    Li ZQ, Kang WL, Tang SJ, et al.

    Journal of obstetrics and gynaecology : the journal of the Institute of Obstetrics and Gynaecology 2023; (43(2)):2287125 doi:10.1080/01443615.2023.2287125.

    PMID: 38069630
  11. 11

    Clinical performance of non-invasive prenatal served as a first-tier screening test for trisomy 21, 18, 13 and sex chromosome aneuploidy in a pilot city in China.

    Liu Y, Liu H, He Y, et al.

    Human genomics 2020; (14(1)):21 doi:10.1186/s40246-020-00268-2.

    PMID: 32503639
  12. 12

    Placental, maternal, fetal, and technical origins of false-positive cell-free DNA screening results.

    Raymond Y, Fernando S, Menezes M, et al.

    American journal of obstetrics and gynecology 2024; (230(4)):381-389 doi:10.1016/j.ajog.2023.11.1240.

    PMID: 38008147
  13. 13

    Analysis of the accuracy of Z-scores of non-invasive prenatal testing for fetal Trisomies 13, 18, and 21 that employs the ion proton semiconductor sequencing platform.

    Tian Y, Zhang L, Tian W, et al.

    Molecular cytogenetics 2018; (11()):49 doi:10.1186/s13039-018-0397-x.

    PMID: 30159034
  14. 14

    Confined placental mosaicism of Duchenne muscular dystrophy: a case report.

    Winerdal M, Westenius E, Granfors M, et al.

    Molecular cytogenetics 2020; (13(1)):51 doi:10.1186/s13039-020-00520-3.

    PMID: 33334361
  15. 15

    [False positive non-invasive prenatal testing results due to vanishing twins].

    Yu T, Li S, Zhao W, Yu D

    Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics 2019; (36(4)):327-330 doi:10.3760/cma.j.issn.1003-9406.2019.04.009.

    PMID: 30950018
  16. 16

    Perinatal and Peripartum Outcomes in Vanishing Twin Pregnancies Achieved by In Vitro Fertilization.

    Romanski PA, Carusi DA, Farland LV, et al.

    Obstetrics and gynecology 2018; (131(6)):1011-1020 doi:10.1097/AOG.0000000000002595.

    PMID: 29742658
  17. 17

    Retrospective details of false-positive and false-negative results in non-invasive prenatal testing for fetal trisomies 21, 18 and 13.

    Suzumori N, Sekizawa A, Takeda E, et al.

    European journal of obstetrics, gynecology, and reproductive biology 2021; (256()):75-81 doi:10.1016/j.ejogrb.2020.10.050.

    PMID: 33171421
  18. 18

    Clinical Review of Noninvasive Prenatal Testing: Experience from 551 Pregnancies with Noninvasive Prenatal Testing-Positive Results in a Tertiary Referral Center.

    Wu X, Li Y, Xie X, et al.

    The Journal of molecular diagnostics : JMD 2020; (22(12)):1469-1475 doi:10.1016/j.jmoldx.2020.09.008.

    PMID: 33069877
  19. 19

    Next-generation sequencing: a follow-up of 36,913 singleton pregnancies with noninvasive prenatal testing in central China.

    Lu W, Huang T, Wang XR, et al.

    Journal of assisted reproduction and genetics 2020; (37(12)):3143-3150 doi:10.1007/s10815-020-01977-2.

    PMID: 33094428
  20. 20

    Clinical features and pregnancy outcomes of women with abnormal cell-free fetal DNA test results.

    Zhou Q, Zhu ZP, Zhang B, et al.

    Annals of translational medicine 2019; (7(14)):317 doi:10.21037/atm.2019.06.57.

    PMID: 31475187
  21. 21

    The role of non-invasive prenatal testing and ultrasound in prenatal screening of fetal chromosomal abnormalities in singleton: a retrospective study.

    Yuan X, Yong W, Dai L, et al.

    Annals of translational medicine 2023; (11(2)):111 doi:10.21037/atm-22-6343.

    PMID: 36819517
  22. 22

    Chromosomal Microarray Analysis in Fetuses with Ultrasound Abnormalities.

    Chen X, Lan L, Wu H, et al.

    International journal of general medicine 2024; (17()):3531-3540 doi:10.2147/IJGM.S472906.

    PMID: 39161407
  23. 23

    Fetal loss following invasive prenatal testing: a comparison of transabdominal chorionic villus sampling, transcervical chorionic villus sampling and amniocentesis.

    Niederstrasser SL, Hammer K, Möllers M, et al.

    Journal of perinatal medicine 2017; (45(2)):193-198.

    PMID: 27416616
  24. 24

    Chorionic Villus Sampling in the Era of Genomic Medicine: A Gateway to Early and Personalized Prenatal Diagnosis.

    Wysocka U, Stępniewska J, Kozłowska M, et al.

    The application of clinical genetics 2026; (19()):567210 doi:10.2147/TACG.S567210.

    PMID: 41560845
  25. 25

    Reply.

    Scott F,

    Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology 2023; (62(4)):612-613 doi:10.1002/uog.27471.

    PMID: 37787001
  26. 26

    The type of feto-placental aneuploidy detected by cfDNA testing may influence the choice of confirmatory diagnostic procedure.

    Grati FR, Bajaj K, Malvestiti F, et al.

    Prenatal diagnosis 2015; (35(10)):994-8 doi:10.1002/pd.4659.

    PMID: 26211640
  27. 27

    Diagnostic testing after positive results on cell free DNA screening: CVS or Amnio?

    Mardy AH, Norton ME

    Prenatal diagnosis 2021; (41(10)):1249-1254 doi:10.1002/pd.6021.

    PMID: 34386984

This page provides educational information about NIPT screening results and does not constitute medical advice. Always consult your obstetrician, maternal-fetal medicine specialist, or a genetic counselor to interpret your specific prenatal test results.

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