What is Trisomy 21 & how is it Diagnosed?

Trisomy 21 is the most prevalent chromosomal anomaly in human beings, also referred to as Down Syndrome, Trisomy 21 is a genetic condition that's characterised by an extra chromosome.

Healthy babies inherit 23 chromosomes from both their mother and father, making 46 in total. However, babies with Down syndrome have three chromosomes at position 21 (hence the name), rather than the typical pair found there.

How is Trisomy 21 Diagnosed?

While it's not mandatory to get tested for Down Syndrome, meaning it's entirely your choice, prenatal screening can be offered to every pregnant woman. The most common manner of offering screening tests nowadays is NIPS – Non-Invasive Prenatal Screening.

These prenatal tests don't tell you whether your fetus has Down Syndrome but rather estimate the probability based on analysis of fetal DNA circulating in the Mother's bloodstream. Tests of this nature are generally offered from about 11 weeks of pregnancy. Remember these are screening tests. Only definitive diagnostic tests offer near-100% accuracy.

The definitive diagnostic procedures that exist for Down Syndrome prenatal diagnosis are amniocentesis and villous sampling (CVS). There is a 1% risk of a spontaneous miscarriage associated with these tests, but if analysed with appropriate skill and experience, they are almost 100% accurate in the diagnosis of Down Syndrome.

On the one hand, amniocentesis is usually carried out between weeks 15 and 22 of gestation, whereas on the other CVS is performed between weeks 12 and 14.

Talk to the Genetics.ie Team About Trisomy 21 Screening

If you're in need of prenatal Trisomy 21 screening, the Genetics.ie team can help. Working from our Blackrock clinic under the supervision of the highly experienced Dr Willie Reardon, we carry out Down Syndrome testing that meets the very highest standards of accuracy and patient care.

To find out more, visit us today at www.genetics.ie where you'll find details of our full range of genetic testing services. Alternatively, to speak to us about Trisomy 21 screening, give us a call on 087 4037149, and we'll be happy to help in any way we can.