Frequently asked questionsA non-invasive prenatal test (NIPT) is a blood test of the mother that estimates the chance of selected chromosome conditions being present in her developing baby. Every person has millions of tiny DNA fragments in the bloodstream. 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. Standard NIPT The main purpose of NIPT is to screen for three common chromosome conditions:
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 is 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 advice about this. Assessment for these trisomies is the most accurate NIPT. NIPT can also screen 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 screen for the presence of more or less than two sex chromosomes for no additional charge. This includes screening for:
These sex chromosome conditions are usually clinically milder than the common trisomies. NIPT can also detect other abnormalities in the number of sex chromosomes (XXX and XYY) that have little impact on a person’s growth and development. The links provide more information. As a separate option, NIPT can also screen for the presence of DNA from a Y chromosome (the male chromosome), indicating the sex of the developing baby. Note that the result of screening the sex chromosomes may indicate the sex of the developing baby, regardless of whether screening for the fetal sex is selected. In a twin pregnancy, the presence of DNA from a Y chromosome is interpreted as there being one or two male fetuses. Assessment of sex chromosomes by NIPT is very accurate, but not as accurate as standard NIPT. Standard NIPT with optional genome-wide NIPTNIPT can also screen for two other types of chromosome abnormality:
Please note that the NIPT provided by Sonic Genetics is a highly accurate screen for specific conditions. It is not a screen for every possible condition that a developing fetus 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 conventional blood tests. It is much better at correctly identifying whether the baby has, or does not have, the condition being screened. 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 fetus. However, NIPT is not perfect. It is still important that your doctor reviews all the relevant tests about your pregnancy, and you may be advised to have additional tests as part of your care. NIPT is a complex and sophisticated test. A more detailed description of the accuracy of NIPT, and how we measure this, can be read here. 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. Collecting a blood sample from you for NIPT poses no threat to your pregnancy. 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 will:
NIPT can screen for the presence of a Y chromosome (the male sex chromosome). This option is available on request from your doctor at no additional cost. If Y chromosome material is detected, this means that the fetus is almost certainly male. If no Y chromosome material is detected, this means that the fetus is almost certainly female. For twin pregnancies, the presence of Y chromosome material indicates the presence of one or two male fetuses. This screening test for fetal sex is correct in more than 99% of pregnancies. However, there is a small chance that the fetal sex determined by NIPT differs from the actual sex of the fetus. This may be due to the placenta and the fetus having different sex chromosomes. This does not harm the fetus. We are pleased to provide a report on the sex of developing fetus at your doctor’s request, but this is not the main purpose of the screen. For the great majority of women screened, NIPT correctly identifies the chromosome status of the developing fetus. However, there are rare instances in which NIPT reports a high chance of a condition and yet the developing fetus is unaffected, or conversely reports a low risk of a condition and yet the fetus is affected. These discrepancies are usually due to the chromosomes in the placenta being different to the chromosomes in developing fetus. The placenta and developing fetus 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 1% 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 fetus and placenta in your blood for NIPT to give an accurate result, or there may be uncommon yet benign variations in certain DNA sequences in the 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). 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. In December 2021, we withdrew the Harmony test for operational reasons. · 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 an increased risk of a chromosome abnormality. The information on this website is provided for your general information and is not a substitute for the specific advice of your treating doctor. |
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