non-invasive prenatal testing

Sisters Marina Fogle and Dr Chiara Hunt investigate non-invasive prenatal testing

Nothing beats the excitement of finding out you’re expecting, but it’s normal for most couples to hold off announcing their news until the end of the first trimester, and once they’ve had results back from their scan and those all-important tests.

All women in the UK are offered a scan at 12 weeks, but many couples choose to take part in additional testing between 11 to 13 weeks, which as yet is not offered on the NHS.

Non-Invasive Prenatal Testing (NIPT) has revolutionised testing in pregnant women. Before 2011, the only screening option was an ultrasound scan and a blood test. If any ‘markers’ for chromosomal abnormalities were detected, the mother would be advised to have an amniocentesis or CVS, where a sample of the amniotic fluid or placenta is taken to determine conclusively whether an abnormality is present. These procedures are invasive, unpleasant for the mother, and also carry with them a one per cent chance of miscarriage.

The genius of NIPT is that it is totally non-invasive; all it requires is a straightforward blood test. Through a sample of the mother’s blood, the lab can detect fragments of the baby’s DNA and look for abnormalities in the chromosomes. Because it’s only 99 per cent accurate (therefore not diagnostic), if the doctor does detect abnormalities, you would be advised to have an amniocentesis or CVS to absolutely determine whether your baby is affected.

NIPT has been a roaring success, so much so that many NHS Trusts hope to be able to offer the service by the end of the year. In the meantime, if you wanted to have this done, you would have to do it privately. It’s offered by clinics around the UK and typically costs between £350 and £500. It should always be performed in conjunction with a scan to confirm whether you’re carrying multiples (this can affect the efficacy of the test) and to check the foetus is alive, as the foetal DNA can stay in the mother’s blood after miscarriage.

Since the dawn of NIPT, an array of labs have offered their versions or brands of the test. The most widely recognised is the Harmony test but there are now a plethora of others available which often confuse parents-to-be. All NIPT tests for the three major chromosomal abnormalities – Down’s, Edwards’ and Patau’s syndrome. There are other brands on the market that test for other, rarer abnormalities that it might be wise to have depending on your family history, if you are carrying multiples, if you have had previous pregnancy complications or specific markers flagged by a scan. Our advice is to find a professional you can trust, have an initial scan and then, based on the findings, take advice on which is best suited to you.

While this innovation provides reassurance for many couples, it also raises a lot of ethical questions. Some of the abnormalities that these tests bring to light are not guaranteed to affect a child in a life-changing way. Before you do the test, it’s worth having the conversation about what you would do in the event that a specific diagnosis is made. Counselling should be available in this situation, but in the end, whether or not you decide to continue with your pregnancy is up to you.

Dr Chiara Hunt and Marina Fogle are founders of The Bump Class, which provides antenatal classes in South West London. Check out the sisters’ podcast, The Parent Hood, available on iTunes and Acast. Visit thebumpclass.com

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