What is a Non-Invasive Prenatal Test?
The last few years have seen the development of Non-Invasive Prenatal Tests (NIPTs) which give information about a baby’s chromosomes; prenatal genetic testing can be performed from early in the pregnancy to offer reassurance as well as a risk assessment of some developmental abnormalities which can affect a pregnancy.
Non-invasive prenatal testing has the advantage of being quick, safe and easy, and can be performed as early as week 9 of pregnancy. It carries no risk to either mother or baby. All that is required is a sample of the mother’s blood. Results are on average back in 5 days from blood draw.
Until recently, when the risk of abnormal development was deemed to be high, the most reliable way to gather definitive information about a baby's genetic makeup was amniocentesis: this procedure involves introducing a very fine needle through the mother's abdomen and into the amniotic fluid around the baby to withdraw some fluid and allow analysis of the cells. Although an amniocentesis produces clear results, it does carry a small risk of miscarriage.
It is important to note that all NIPTs have limitations: they are “screening” tests, as opposed to “diagnostic” tests. They evaluate the risk (not the certainty) of a baby having some genetic abnormality. No result, to this day, is 100% accurate. A small risk of “false positive” and “false negative” results does exist, regardless of which NIPT you choose. Prenatal DNA testing is not meant to be the sole test on which to base decisions about a pregnancy, particularly when there is a positive result (when the report shows some findings of potential anomalies). In such cases, the recommendation is to undertake further tests, such as amniocentesis or CVS, as well as genetic counselling.
The most widely known condition resulting from genetic abnormality is Down syndrome. This is one of a range conditions known as 'trisomy' (where there are three copies of a chromosome instead of the usual two) that result in physical defects, some of which may be life threatening, and can be tested for during pregnancy. Here you can learn more about congenital conditions related to chromosome abnormalities.
At The Medical Chambers Kensington, we are proud to offer patients a choice of screening tests, alongside our expert pregnancy ultrasound service. Dr Nyberg, who runs the Ultrasound Clinic, has been using NIPTs since their inception in the USA. As technology develops and more sophisticated tests become available, we are keen to offer a variety of tests, which allows patients to make an informed choice on what is best for them, the information they wish to have, their medical or family history etc.
Why choose to have a prenatal blood test at The Medical Chambers?
Usually a chromosomal test in pregnancy is requested where a significant risk of chromosome abnormality has been calculated. This will be based on consideration of maternal age, personal medical history, family or genetic history, and results of pregnancy scan. We recommend you discuss your personal situation with your doctor or prenatal specialist.
You may also request one of these tests if you wish to have reassurance that everything is developing normally. Chromosome analysis during pregnancy is not yet routine in the UK but is increasingly becoming more common. As a private clinic we are here to meet your needs, whatever your personal or family background. We do not require referral from your doctor.
Most NIPTs can assess the risk of Trisomy 21 (Down Syndrome); Trisomy 18 (Edwards Syndrome) and Trisomy 13 (Patau Syndrome). You can learn more about these conditions by clicking on the link below. The accuracy of NIPTs for assessing the risk of Down Syndrome is over 99%; by comparison, the “classic” combined test (12 week nuchal scan + PAPPA blood test) has an accuracy of 75 to 80%.
More recent advances in prenatal DNA testing allow to screen for other congenital conditions and physical or developmental abnormalities. Tests such as MaterniT21 PLUS look at specific microdeletions linked to known specific syndromes (Di George, Cri Du Chat etc…), whereas MaterniT GENOME analyses every single chromosome of your baby, giving you a level of information close to a karyotype.
How to choose the right prenatal blood test?
Everyone is different and it is important that you make the right choice of test. In Dr Nyberg’s words: “The best test is the one that is right for you”. It is the test that will give you the level of reassurance you need and the level of information you desire. We help you make this choice by giving you as much information as we can and answering your questions so that you can make the right decision. To make it easier to understand the difference between the various tests we offer, we have summarised them in the following chart.
Can I have a non-invasive prenatal blood test without a scan at The Medical Chambers Kensington?
Our gold standard is to make sure that we proceed with your chosen test only if all is going well at that point in your pregnancy. So we always try to combine a viability or early pregnancy scan (10-11 weeks) or a 12 weeks scan (11+3 -> 13+5) with your appointment for the blood draw.
In some cases, we will offer a Non-invasive prenatal test without a scan carried out at The Medical Chambers Kensington. However, if you are less than 13 weeks into your pregnancy, we will ask you to bring the report of your most recent scan, which will have to be no more than 4 days before your blood draw. Again, this is for peace of mind: yours and ours!