Cell free DNA (Non Invasive Prenatal Testing – NIPT)
What Is Non-Invasive Prenatal Testing (NIPT)?
Non-invasive prenatal testing (NIPT), also known as cell-free DNA (cfDNA) screening, is a simple blood test performed during pregnancy to screen for certain chromosomal conditions in the baby, such as Down syndrome (trisomy 21).
During pregnancy, small fragments of DNA from the placenta enter the mother’s bloodstream. NIPT analyzes this placental DNA to estimate the chance that the fetus has specific chromosomal abnormalities. Because it only requires a maternal blood sample, the test carries no risk to the pregnancy.
What Can NIPT Screen For?
Depending on the laboratory platform, NIPT can screen for:
Common chromosomal conditions
– Down syndrome (trisomy 21)
– Edwards syndrome (trisomy 18)
– Patau syndrome (trisomy 13)
Sex chromosome conditions (e.g., Turner syndrome – 45,XO; Klinefelter syndrome – 47,XXY; Triple X syndrome – 47,XXX; and others)
Fetal sex (male or female)
Selected microdeletion syndromes (e.g., 22q11.2 deletion/DiGeorge syndrome, 5p deletion/Cri-du-chat syndrome, 1p36 deletion syndrome)
Important note on microdeletions: Although some NIPT tests include microdeletion screening, major professional societies (including ACOG and SMFM) do not recommend routine screening for these conditions in the general population. They are rare and the positive predictive value is lower than for the common trisomies, meaning a “positive” result is more likely to be a false alarm. Expanded microdeletion screening should only be considered after detailed counseling and individualized risk assessment.
Some specialized platforms can also determine fetal Rh status or perform paternity testing (when both parents’ samples are provided). Always discuss the accuracy and limitations of any expanded panel with your doctor before testing.
How Accurate Is NIPT?
NIPT is currently the most accurate screening test available for the common chromosomal abnormalities:
– Down syndrome (trisomy 21): >99% detection rate
– Trisomy 18 and trisomy 13: very high detection rates
– Sex chromosome abnormalities: high sensitivity, but lower positive predictive value (higher chance of false positives)
Key point: NIPT is a screening test, not a diagnostic test. The DNA tested comes from the placenta, so rare cases of confined placental mosaicism can lead to false-positive or false-negative results. Any high-risk (“positive”) result must be confirmed with diagnostic testing, such as amniocentesis or chorionic villus sampling (CVS).
NIPT does not screen for all genetic conditions and does not replace the detailed mid-trimester anatomy ultrasound scan.
Can NIPT Tell Me the Baby’s Sex?
Yes. NIPT determines fetal sex with approximately 99% accuracy. In very rare cases, results may differ due to placental mosaicism or technical factors.
What Does a “Positive” (High-Risk) NIPT Result Mean?
A positive result means the fetus has a higher chance of the specific chromosomal condition — it is not a confirmed diagnosis.
The actual likelihood that the result is a true positive (positive predictive value) depends on:
– Maternal age
– The specific condition
– Your pre-test risk
For example, a positive result for Down syndrome is more likely to be correct in an older mother than in a younger one. Positive results for sex chromosome conditions tend to have lower predictive values.
What Happens After a Positive Result?
Your doctor will:
1. Review your individual risk and gestational age
2. Arrange a detailed ultrasound
3. Provide genetic counseling
4. Offer confirmatory diagnostic testing (usually amniocentesis)
Some babies with chromosomal conditions may have normal or only subtle ultrasound findings, especially early in pregnancy.
What If I Get a “No-Call” (No-Result) Outcome?
In a small percentage of cases (roughly 0.03–11%, depending on the lab and patient factors), NIPT does not return a result. Common reasons include:
– Low fetal fraction (<4%)
– High maternal BMI
– Early gestational age
– IVF pregnancy
– Advanced maternal age
– Laboratory or assay issues
Less commonly, maternal conditions such as certain blood disorders, vitamin B12 deficiency, or heparin use can contribute.
Important: A no-call result itself is associated with a slightly higher risk of certain chromosomal abnormalities (especially trisomies 13, 18, and triploidy).
What should you do after a no-call?
Your doctor will individualize the plan. Options usually include:
– A detailed ultrasound
– Repeating the NIPT (a second draw gives a result in ~75–80% of cases)
– Diagnostic testing (amniocentesis or CVS), depending on gestational age and clinical findings
Is It Important Where I Do My NIPT?
Yes. Because NIPT results can lead to important decisions, it is best to have the test with a provider who offers:
– Clear pretest and post-test genetic counseling
– Prompt access to confirmatory diagnostic testing
– Continuity of care
Choosing an experienced prenatal genetics provider helps ensure you receive accurate explanations and evidence-based support.
References
1. Rink BD, Dugoff L, Kuller JA, et al.; Society for Maternal-Fetal Medicine Publications Committee. Society for Maternal-Fetal Medicine Consult Series #74: Cell-free DNA screening for aneuploidies: updated guidance. Pregnancy. 2025;1(6):e70139. doi:10.1002/pmf2.70139.
2. American College of Obstetricians and Gynecologists. Screening for fetal chromosomal abnormalities. Practice Advisory. January 2026. Available from: https://www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2026/01/screening-for-fetal-chromosomal-abnormalities. Accessed March 7, 2026.
3. Gil MM, Quezada MS, Revello R, Akolekar R, Nicolaides KH. Analysis of cell-free DNA in maternal blood in screening for fetal aneuploidies: updated meta-analysis. Ultrasound Obstet Gynecol. 2015;45(3):249-66. doi:10.1002/uog.14706.
4. Gregg AR, Skotko BG, Benkendorf JL, et al. Noninvasive prenatal screening for fetal aneuploidy: 2016 update—a position statement of the American College of Medical Genetics and Genomics. Genet Med. 2016;18(10):1056-65. doi:10.1038/gim.2016.97.
Maternal–Fetal Medicine Specialist in Bangkok
Dr. Narisra Srikureja Firer (Dr. Niti)
Dr. Niti is a Bangkok-based OBGYN with subspecialty training in Maternal–Fetal Medicine (MFM). She provides comprehensive care for women across all stages of life, including pregnancy care, deliveries, and general gynecological conditions.
She dedicates her time to private practice at Ruamjairak Hospital and Mission Hospital, and serves as a Maternal–Fetal Medicine Consultant at a large government tertiary care center.
To read Dr. Niti’s full bio, click here.
