Frequently asked questions
A non-invasive prenatal test (NIPT) is a blood test of the mother that predicts the chance of selected conditions being present in her developing baby.
Every person has millions of tiny DNA fragments in their blood. This is a normal process. In a pregnant woman, most of these fragments come from the mother, and some come from the baby’s placenta. The baby and the placenta grow from the same fertilised egg, and so the placenta’s DNA fragments are almost always the same as those from the developing baby. NIPT works by examining these tiny fragments of DNA in the mother’s blood and determining the chance that the fragments reveal a chromosome condition in the placenta and developing baby.
The main purpose of NIPT is to screen for three common chromosome conditions:
- Down syndrome (trisomy of chromosome 21)
- Edwards syndrome (trisomy of chromosome 18)
- Patau syndrome (trisomy of chromosome 13)
These conditions are caused by the presence of three copies of a particular chromosome (“trisomy”) in every cell of the baby’s body rather than the usual two copies. Each of these conditions causes moderate to profound intellectual disability and are associated with major congenital malformations. The links above provide more information about each syndrome. The chance of a developing baby having one of these syndromes increases with the age of the mother; your doctor can provide you with personal advice about this.
NIPT can also test for abnormal numbers of sex chromosomes. Males usually have an X and a Y chromosome; females have two X chromosomes. On request from your doctor, NIPT can test for the presence of more or less than two sex chromosomes for no additional charge. This includes testing for
- Turner syndrome (having only one sex chromosome, an X)
- Klinefelter syndrome (having three sex chromosomes, two Xs and a Y)
These sex chromosome conditions are often clinically milder than other chromosome conditions. NIPT can also detect other abnormalities in the number of sex chromosomes that may be milder (XXX and XYY). The links above provide more information about these syndromes. We are pleased to provide a report on the number of sex chromosomes of your developing baby at your doctor’s request, but this is not the main purpose of the test. The chance of a developing baby having some of these syndromes increases with the age of the mother; your doctor can provide you with personal advice about this. Testing of the sex chromosomes is less accurate than testing for the trisomies listed above. Testing of the sex chromosomes, if selected as an option and if found to be abnormal, will indicate the sex of the developing baby regardless of the fetal sex option being selected.
NIPT can also test for DiGeorge syndrome (22q11.2 deletion). This option is available at your doctor’s request for an additional fee. This condition is caused by the loss of a small portion of chromosome 22. This syndrome can cause heart defects, poor immune system function, a cleft palate and low levels of calcium in the blood. Its features vary widely, even among people with the same chromosome deletion. The link above provides more information about this syndrome. The chance of a developing baby having this syndrome does not vary with the age of the mother.
Please note that the NIPT provided by Sonic Genetics is a highly accurate test for these specific conditions. It is not a test for every possible condition that a developing baby may have. NIPT is just one of the investigations that your doctor may recommend for you before or during your pregnancy.
NIPT is more accurate than traditional screening tests for chromosome conditions such as ultrasound and older blood tests. It is much better at correctly identifying whether the baby has, or does not have, the condition being tested. This means that your doctor is less likely to recommend an additional invasive test (amniocentesis or chorionic villus sample) to confirm the genetic status of your baby.
However, NIPT is not perfect. It is still important that your doctor reviews all of the relevant tests about your pregnancy, and you may be advised to have additional tests as part of your care.
Your results are typically sent to your doctor in 3–8 business days from the day your blood sample was received in one of our testing laboratories. Occasionally a result is not obtained and a second sample may be requested (at no additional cost), although this is a rare occurrence.
Collecting a blood sample from you for NIPT poses no threat to your baby.
Your doctor will advise you about the tests you should have, and when they should occur. As a general rule, we recommend that a woman have an ultrasound before the blood sample for NIPT is collected. The ultrasound may:
· confirm the stage and viability of the pregnancy; NIPT has not been validated for use before 10 weeks' gestation
· examine for the presence of twins; the laboratory needs to know if you have twins; NIPT has not been validated for use with triplet pregnancies
· identify any important conditions affecting the baby that would not be detected by NIPT
NIPT can test for the presence of a Y chromosome (the male sex chromosome). This option is available on request from your doctor at no additional cost. For twin pregnancies this could indicate either two females (if absent) or at least one male (if present).
We are pleased to provide a report on the sex of your developing baby at your doctor’s request, but this is not the main purpose of the test.
For the great majority of women tested, NIPT correctly identifies the chromosome status of the developing baby. However, there are rare instances in which NIPT reports a high chance of a condition and yet the developing baby is fine, or a very low chance of a condition and yet the developing baby is affected. These discrepancies are usually due to placental DNA being different to the DNA in developing baby. The placenta and developing baby arise from the same fertilised egg, but on rare occasions, a genetic abnormality may occur in one that does not occur in the other.
The chance of an NIPT result being incorrect varies according the condition being considered, the age of the mother, and the results of other tests that may have been ordered by your doctor. It is important that an NIPT be used as just one of the tests being considered by your doctor, and that the result is considered together with other investigations.
In up to 2% of patients, we may not be able to provide an assessment regarding every chromosome condition requested by your doctor. There may be insufficient DNA from the baby and placenta in the mother’s blood for NIPT to give an accurate result, or there may be uncommon yet benign variations in certain DNA sequences in mother or fetus that compromise the accuracy of the test. Depending on the underlying cause, we may recommend a re-collection with reanalysis (at no extra cost to you). In approximately half of those women who have a second collection, we are able to provide a definite result.
If we are unable to provide an assessment regarding the three common trisomies after one sample collection (or after two, if the laboratory requests a second collection), the credit card holder that paid Sonic Genetics for the test will be refunded in full upon request; please contact us on 1800 010 447.
When NIPT first became available in early 2013, we carefully evaluated the performance of different NIPT tests before deciding which test to use in our laboratories. In 2015, we implemented the Harmony® prenatal test in our Brisbane laboratory.
Over the next five years, we became a major provider of NIPT across Australia. During this time, test methods improved. In 2020, we installed a second type of NIPT called VeriSeq NIPT Solution v2 in our Sydney laboratory. Both types of NIPT provide comparable, high quality results and are used extensively throughout the world.
· Our NIPT is supervised by a team of genetic pathologists and medical scientists who can have a detailed discussion with your doctor about your result, should this be required
· A blood sample for our NIPT can be collected from over 400 collection centres across Australia
If you have paid Sonic Genetics or a Sonic Pathology laboratory directly for your NIPT, we offer free telephone-based genetic counselling if you have a result that indicates a high chance of your baby having a chromosome condition.
The information on this website is provided for your general information and is not a substitute for the specific advice of your treating doctor.