NIPT at Beard Mill Clinic
The non-invasive prenatal test (NIPT) is a relatively new method of screening for chromosome abnormalities and works because a tiny amount of the baby’s DNA crosses the placenta into the mother’s blood. So with just a normal blood sample from the mother, the baby’s DNA can be analysed directly and the relative amount of each chromosome assessed.
The commonest chromosome abnormality, Down’s syndrome, can be picked up with over 99% accuracy and it is very unlikely that you will be given an abnormal result unless there really is an issue.
It is particularly useful for older mothers who are at higher risk because of their age, or for those who have had normal first trimester screening already and have been given a high risk result - or for those who just need a bit more reassurance. However it must be stressed that the test is not diagnostic and that a low-risk result does not mean that there is absolutely no risk and a high-risk result will still need an invasive test to provide certainty.
Different laboratories have given the test different brand names, so you may hear the test referred to as the Harmony™ Prenatal test or the Iona test, but the concept behind these tests is the same. Beard Mill Clinic currently uses the Harmony™ Prenatal Test.
What else does the Harmony™ Prenatal Test pick up?
The Harmony™ Prenatal Test has been developed specifically as a screening test for Down’s syndrome. However the same genetic sequencing techniques can be used to analyse two additional chromosomes - chromosome 18 and chromosome 13 - and the Harmony™ Prenatal Test will look at the risk of Edwards’ syndrome (where the baby has an extra copy of chromosome 18) and Patau’s syndrome (an extra copy of chromosome 13) too. The results so far suggest that the pick-up rates aren’t quite so good as the Down’s syndrome detection rates (98% for Edwards’ syndrome and 80% for Patau’s syndrome), but these babies usually have abnormalities that can be seen on ultrasound scan, so certain ultrasound features will always heighten suspicion, regardless of a normal Harmony™ Prenatal Test and will rarely be missed.
If you want to know, the Harmony™ Prenatal Test will also identify the baby’s gender, but this will not be disclosed if you don’t wish to find out.
Do I need a scan too?
At Beard Mill Clinic, we believe that the non-invasive prenatal test should always be done in combination with a thorough scan. The test can be used in multiple pregnancies, but not if one twin stopped developing at an early stage (a vanishing twin), so it is important to have a scan to check this. A good 12-week scan will occasionally pick-up a severe structural abnormality, such as spina bifida or a diaphragmatic hernia, and an increased nuchal translucency measurement is also a marker for a wide range of conditions other than Down’s syndrome. It is therefore essential that the NIPT results are always looked at in the context of the 12-week scan findings and never in isolation and it is important not to miss out on this important scan.
Just occasionally, something may be seen on scan which would mean that it may be more appropriate to do an invasive test (such as an amniocentesis) instead of NIPT. Therefore even if you are thinking about having the test after 12 weeks and have already had a nuchal translucency scan, a detailed scan at Beard Mill Clinic is still recommended to make sure that NIPT is the best test for you to have.
When can I have NIPT?
The NIPT blood test can be done from 10 weeks onwards, but it is more accurate if there is more DNA, so it is better to wait until 11 weeks if you can. There is no upper limit to performing the test.
Therefore if you decide early on in your pregnancy that you will have NIPT, Beard Mill Clinic offers a package of having the blood test (and a quick scan) done at 11 weeks and then coming back at 12 weeks for the detailed nuchal scan and an explanation of all the results.
If the pregnancy is more than 11 weeks when you decide to have the test done, an in depth scan will be done at the same time as the blood test - the level of detail will be appropriate for the stage you are at in the pregnancy - and then you will be contacted (usually by phone) with the NIPT results as soon as they are available. The results are currently taking about 5 working days to come through.
Can anyone have NIPT?
Anyone can choose to have NIPT and can contact Beard Mill Clinic directly. A referral from your GP is not required.
It can be performed in all single and twin pregnancies, including those conceived by IVF, even if donor eggs are used. The only exceptions are if the mother herself has an unusual chromosome rearrangement or if there has been a vanishing twin (see above).
Just occasionally the analysis of the sample fails because insufficient cell-free DNA is extracted. In this situation, the mother will be asked to provide a second blood sample at no additional cost.