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A non-invasive prenatal test (NIPT) can help screen for the likelihood of certain chromosomal conditions in a developing baby. This test may provide expectant mothers with useful information about their baby's health early in pregnancy, offering reassurance when results indicate a lower risk or helping them prepare for further assessment when needed.
Understanding what NIPT can do may help you make an informed decision about testing during pregnancy. This article covers what NIPT screens for, who may consider it and how obstetricians explain the possible results to you.
Key Takeaways
- NIPT is a non-invasive blood test that can screen for the likelihood of certain chromosomal conditions
- It primarily screens for Down syndrome, Edwards syndrome and Patau syndrome, while some NIPT panels can screen for additional chromosomal conditions.
- NIPT may be considered by pregnant women who want additional prenatal screening, particularly when certain factors indicate a higher risk of chromosomal conditions.
- A low-risk result indicates a lower likelihood of the conditions screened for, while a high-risk result indicates an increased likelihood.
- NIPT is a screening test, not a diagnostic test. High-risk results may need to be confirmed through diagnostic testing such as amniocentesis or CVS.
What Is NIPT and How Does It Work?
NIPT is a prenatal blood test that screens for the likelihood of certain chromosomal conditions in a developing baby. It analyses small fragments of cell-free DNA (cfDNA) from the placenta that circulate in the mother's bloodstream during pregnancy.
The test requires a blood sample from the mother and can generally be performed from 10 weeks of pregnancy. The sample is analysed to look for differences in the amount of DNA associated with particular chromosomes, which can indicate an increased or decreased likelihood of certain chromosomal conditions.
As NIPT only requires a maternal blood sample, it does not carry the procedure-related miscarriage risk associated with invasive diagnostic tests such as chorionic villus sampling (CVS) or amniocentesis.
What Does NIPT Screen For?
NIPT primarily screens for the likelihood of three common chromosomal conditions:
- Down syndrome (Trisomy 21): Caused by an extra copy of chromosome 21 and associated with characteristic physical features and varying degrees of intellectual disability.
- Edwards syndrome (Trisomy 18): Caused by an extra copy of chromosome 18 and associated with serious developmental and health problems.
- Patau syndrome (Trisomy 13): Caused by an extra copy of chromosome 13 and associated with serious abnormalities affecting development and multiple parts of the body.
Depending on the type of NIPT performed, screening may also provide information about other chromosomal conditions.
Sex Chromosome Abnormalities
Some NIPT options can screen for abnormalities involving the sex chromosomes. The test can also determine the baby's sex before this can typically be identified through an ultrasound.
Triploidy
NIPT may screen for triploidy, a chromosomal condition in which the developing baby has an additional complete set of chromosomes. Triploidy can affect growth and development and is associated with significant pregnancy complications.
Microdeletion Syndromes
Certain NIPT options can also screen for microdeletions, where a small piece of a chromosome is missing. These include conditions such as DiGeorge syndrome, Angelman syndrome, Cri-du-chat syndrome and Prader-Willi syndrome.
What Does NIPT Not Screen For?
NIPT does not provide a complete assessment of a baby's health or detect every possible genetic, chromosomal or physical condition. The conditions included also vary according to the specific NIPT panel being used.
Importantly, NIPT is a screening test rather than a diagnostic test. Its results indicate whether there is a higher or lower likelihood of the conditions being screened for but cannot confirm a diagnosis. A higher-risk result may therefore be followed by diagnostic testing such as amniocentesis or chorionic villus sampling (CVS).
Who Should Consider NIPT?
NIPT may be considered by pregnant women who want additional screening for certain chromosomal conditions, particularly those with a higher likelihood due to maternal age, previous screening results, ultrasound findings or pregnancy history.
Your doctor may recommend discussing NIPT if:
- You are of advanced maternal age, as the likelihood of certain chromosomal conditions increases with age.
- Earlier prenatal screening indicates a higher risk of a chromosomal condition.
- An ultrasound identifies a potential concern that may require further assessment.
- You have had a previous pregnancy affected by a chromosomal condition.
- You want additional prenatal screening, even without known risk factors.
How Do Obstetricians Interpret Your NIPT Results?
NIPT results are generally interpreted as showing a low or high risk of the chromosomal conditions screened for, while some tests may return an inconclusive result. As NIPT is a screening test, these results estimate likelihood rather than confirm or rule out a particular condition.
What Does a Low-Risk NIPT Result Mean?
A low-risk result means the test found a lower likelihood of the baby having the chromosomal conditions screened for. While this can be reassuring, it does not completely rule out these conditions or other genetic and developmental problems that NIPT does not screen for.
What Does a High-Risk NIPT Result Mean?
A high-risk result means the test has identified an increased likelihood of a particular chromosomal condition. It does not confirm that the baby has the condition, so your obstetrician may discuss diagnostic testing such as amniocentesis or chorionic villus sampling (CVS) to confirm the result.
What Does an Inconclusive NIPT Result Mean?
An inconclusive result means the test was unable to provide a clear assessment. This can happen when there is insufficient cell-free DNA in the blood sample or for other clinical reasons. Your obstetrician can assess the result in the context of your pregnancy and advise whether repeat NIPT, further assessment or diagnostic testing is appropriate.
How Can I Make an Informed Decision About NIPT During Pregnancy?
NIPT can provide useful information about the likelihood of certain chromosomal conditions early in pregnancy, but whether it is appropriate for you depends on your individual circumstances, what you want to learn from screening and how you would approach the possible results. An experienced obstetrician can explain how NIPT fits into your prenatal care, assess whether it is appropriate for your pregnancy and help you understand the implications of the possible results.
At GynaeMD Women’s & Rejuvenation Clinic, Consultant Obstetrician & Gynaecologist Dr Christopher Ng provides personalised prenatal care and guidance on screening options such as NIPT. He takes the time to discuss your individual circumstances, explain the available options clearly and guide you through the next steps based on your results.
If you are considering NIPT or any other type of pregnancy screening, contact us today to arrange a consultation.
Frequently Asked Questions About NIPT During Pregnancy
When is the best time to do NIPT?
NIPT can generally be performed from 10 weeks of pregnancy onwards. Having the test early in pregnancy can provide information about the likelihood of certain chromosomal conditions and allow time to discuss any further assessment that may be needed based on the results.
Is NIPT safe for the mother and baby?
Yes. NIPT only requires a blood sample from the mother and does not involve inserting a needle into the uterus or placenta. As a non-invasive screening test, it does not carry the procedure-related miscarriage risk associated with diagnostic tests such as amniocentesis or CVS.
Do I still need pregnancy ultrasounds after NIPT?
Yes. NIPT does not replace routine pregnancy ultrasounds because it only screens for specific chromosomal conditions. Ultrasounds provide different information about the baby's growth, anatomy and development, making them an important part of prenatal care even after a low-risk NIPT result.
Can NIPT detect birth defects?
NIPT does not screen for all birth defects. It is designed to assess the likelihood of specific chromosomal conditions included in the chosen test panel. Other structural or developmental concerns may instead be identified through pregnancy ultrasounds and other prenatal assessments.
