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NIPT analyses fragments of fetal DNA in the mother’s blood to detect chromosomal conditions including Down’s syndrome. It can be carried out from 10 weeks gestation and has a sensitivity of over 99 percent. This guide explains how it works, its accuracy and what a positive result means.
Non-Invasive Prenatal Testing, commonly known as NIPT, is a prenatal screening test that analyses fragments of fetal DNA present in the mother’s blood to detect chromosomal conditions including Down’s syndrome, Edwards’ syndrome and Patau’s syndrome. NIPT can be performed from 10 weeks of gestation and has a sensitivity of over 99 percent for Down’s syndrome, making it significantly more accurate than the NHS combined test. On the NHS, NIPT is offered as a second-stage test to women who have received a high-chance result from the combined test. Private NIPT is available to any pregnant woman from 10 weeks gestation without requiring a prior high-chance result.
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During pregnancy, small fragments of DNA from the placenta circulate in the mother’s bloodstream. These cell-free DNA fragments reflect the chromosomal composition of the fetus and can be analysed from a simple maternal blood sample. NIPT sequences and analyses these DNA fragments to identify whether there is an excess of chromosome 21 material, which would indicate Down’s syndrome. Because the test uses the mother’s blood rather than sampling fetal or placental tissue directly, it carries no risk of miscarriage.
NIPT has a sensitivity of over 99 percent for detecting Down’s syndrome in singleton pregnancies, meaning it correctly identifies the vast majority of affected pregnancies. It also has a very low false positive rate. AlphaBiolabs confirms its NIPT test detects 97.2 percent to 100 percent of trisomies in singleton and twin pregnancies. Despite this high accuracy, NIPT remains a screening test rather than a diagnostic test, and a positive result must be confirmed by amniocentesis or CVS before clinical decisions are made.
On the NHS, NIPT is offered to women who have received a high-chance result from the combined screening test, as a step between screening and invasive diagnostic testing. Private NIPT is available to any pregnant woman from 10 weeks gestation and can be accessed without a prior high-chance combined test result. Private providers include specialist laboratories and some private clinics. The NHS NIPT result is provided through the maternity care team; private results may be provided directly or through a clinician.
A positive NIPT result for Down’s syndrome means the test has detected an elevated proportion of chromosome 21 DNA, indicating a high probability that the pregnancy is affected by Down’s syndrome. It is not a definitive diagnosis: a small number of positive NIPT results are false positives, meaning the baby does not actually have Down’s syndrome. A positive NIPT result should always be followed by an offer of a diagnostic test, either amniocentesis or CVS, to confirm the chromosomal result before any decision is made about the pregnancy.
A negative NIPT result significantly reduces the probability of Down’s syndrome but does not eliminate it entirely. The false negative rate for NIPT is very low but not zero. Rare chromosomal arrangements and confined placental mosaicism can occasionally lead to a false negative result. Women who receive a negative NIPT result but continue to have concerns, or who have additional ultrasound findings that suggest a chromosomal condition, should discuss these with their clinician.
NIPT can be performed in twin pregnancies but is more complex than in singleton pregnancies because the DNA from both fetuses is present in the maternal blood. Sensitivity may be slightly lower in twin pregnancies. In identical twin pregnancies, a positive NIPT result would be expected to apply to both twins. In non-identical twin pregnancies, it may not be possible to determine from NIPT which twin is affected. Specialist advice should be sought when NIPT is being considered in a multiple pregnancy.
For related information see our articles on Down’s Syndrome Pregnancy Screening and Down’s Syndrome Diagnosis.
NIPT is a prenatal screening test that analyses fetal DNA in the mother’s blood. It can detect Down’s syndrome with a sensitivity of over 99 percent, making it significantly more accurate than the NHS combined test. However, it remains a screening test rather than a diagnostic test: a positive result should always be confirmed by amniocentesis or CVS before any clinical decision is made.
Yes, but with a restriction. On the NHS, NIPT is offered as a second-stage test to women who have received a high-chance result from the combined screening test. It is not offered routinely to all pregnant women on the NHS. Private NIPT is available to any pregnant woman from 10 weeks gestation without requiring a prior high-chance result.
If you receive a positive NIPT result for Down’s syndrome, you should be offered an appointment with a specialist, typically a fetal medicine consultant or specialist midwife, to discuss the result and the options available. These options include proceeding to amniocentesis or CVS to confirm the diagnosis and obtaining more information before deciding whether to continue the pregnancy. The Down’s Syndrome Association can provide support and information at this stage regardless of what decision you are considering.
Visit our Understanding Down’s Syndrome hub for more guides on causes, diagnosis, education, health conditions and independent living.
The information in this article is provided for educational purposes only and is not intended as medical advice. If you have concerns about Down’s syndrome or any health condition, speak to a qualified healthcare professional. SENDhelp Education Limited accepts no responsibility or liability for any loss or damage arising from reliance on this content. Any links to third-party websites are provided for convenience only and do not constitute endorsement of their content.
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