Home Health Everything You Need to Know About Trisomy 21 and Prenatal Testing

Everything You Need to Know About Trisomy 21 and Prenatal Testing

by Rohan Mathew
Everything You Need to Know About Trisomy 21 and Prenatal Testing

Down syndrome is a condition that develops genetically. The major cause of Down syndrome is the presence of an extra pair of the 21st chromosome. 

People with Down syndrome are exposed to risks of developing cognitive impairment and may also experience unwanted delays in their development. 

If you belong to the maternal age group above 35, you may refer to 24/7 pharmacies to get a quick guide on supplements or vitamins to minimize the risk of Down syndrome in pregnancy.

There are certain physical traits that are common among those diagnosed with Down syndrome. A poor muscle tone, a crease on the palm, a flat nose bridge, and a slant of the eyes are common although not necessary. 

Not all children diagnosed with Down syndrome may have all the above described physical traits.

Since the problem is rooted in genetics, it is essential to bring to our knowledge that Down syndrome does not occur due to any specific socio-economic orientation. It does not have to do anything with any particular culture, ethnicity, or region. In the United States, 1 out of 1000 births is posed with the risk of Down syndrome.

Common Causes

Some common causes of Down syndrome are:

Translocation is one of the most common causes of Down Syndrome. The extra 21st chromosome is carried by a parent in a hidden way. The extra 21st chromosome falls into the other chromosome. Around 3 to 4 percent of Down syndrome cases are caused by translocation.

More than 90 percent of cases of Down syndrome emerge because of trisomy 21. Trisomy 21 implies that the fetus carries 3 pairs of the 21st chromosome. Normally, 23 pairs of chromosomes are what everyone has. 

Chromosomes normally spit during the formation of the egg. However, when trisomy 21 occurs, the chromosome pairs do not split. Rather, they pair up further, adding extra to the sperm and the egg.

Another condition for an extra part of the 21st chromosome is mosaicism. When mosaicism takes place, a child may not have the extra part of the 21st chromosome in all their cells.

However, since the extra is added to a few cells, the likelihood of Down syndrome is still there. Around 1 to 2 percent of cases pertaining to Down syndrome are caused by mosaicism.

If you’re curious about what is the prime cause of Down syndrome, then you must know that age is the major defining factor in this matter. The maternal age is directly associated with the risk of developing Down Syndrome.

There are varying degrees of risks involved with various age groups;

  • Mothers under age 25 have a chance of giving 1 out of 1,400 births of Down Syndrome
  • The risk amplifies slightly among mothers aged 35 and above as they have a chance of giving 1 birth of Down syndrome out of 350
  • The risk is significant among mothers aged 40 and above. The odds of a baby having Down syndrome are 1 out of 100

Prenatal Testing

Testing for Down Syndrome beforehand can help you to mitigate against these complications. A suitable approach is prenatal testing. There are two types of testing methodologies that apply to Down Syndrome testing.

You could get screen-tested for Down syndrome. Even though screening tests are excellent in minimizing the risk of miscarriage, they don’t provide a more careful examination of the fetus than diagnostic testing.

Through diagnostic testing, you would be able to examine the fetus in a more detailed manner and identify any underlying problems immediately. However, diagnostic testing has a 1 percent risk of miscarriage.

A screening technique that is common is non-invasive screening. The prenatal period between 10-14 weeks of pregnancy is considered as an ideal time to take a blood sample of the mother. Plus, an ultrasound is performed to measure the fluid present in the baby’s neck. 

The fluid amount, and blood sample in conjunction with maternal age are seen as determinants of the risk of Down syndrome for the baby.

Another critical step in the non-invasive screening test is the maternal blood test. The sample is taken during the start of the second trimester (between 15 and 20 weeks) of the prenatal period.

 Detection is improved by combining the blood test samples of the second trimester with the first. This blood sample could also serve as clearance for personal risk assessment.

Diagnostic Testing

Techniques for diagnostic testing during the prenatal period for Down Syndrome entail amniocentesis, CVS, and ultrasound.

The amniocentesis process is effective for detecting problems with the fetus. It is performed during the second trimester and examines the amniotic fluid for analyzing risks. 

It is considered highly accurate in detecting Down Syndrome in the fetus. Neural tube effects could also be indicated with the tests. In addition, amniocentesis has a miscarriage rate of less than 1 percent.

Another prominent diagnostic testing methodology is CVS. CVS is considered to be more effective than amniocentesis in detecting Down syndrome in the fetus. 

Plus, the benefit of CVS is that the tests could be performed during the first trimester, making it easier to get results early. However, it is essential to note that spinal cord issues are not detectable with this test and there is a small risk of miscarriage with CVS.

Another technique of prenatal testing for Down syndrome is ultrasound. Ultrasound is a prominent procedure for knowing the due date for the delivery, size of the fetus, health, issue if any, and whether the womb is carrying multiple fetuses. 

The benefit of ultrasound is that the results are easily retrieved subsequently after testing. 

What to Do?

If you get a positive feedback

In case you receive a positive result for your initial prenatal screening, it is highly recommended that you consult with your physician and genetic specialist. You may be advised to proceed with further diagnostic testing. You could decide upon whether or not to go for invasive testing.

If you get a negative feedback

However, on the contrary, if your tests receive abnormal results, then it is imperative that the results are discussed carefully with a genetic specialist and your physician. Seek consultation with your doctor at your earliest.

Related Articles

Leave a Comment