When can you tell if you have Trisomy 21 (Down Syndrome)? [Doctor-supervised]

What is Down Syndrome?

Down syndrome is officially called ” Down syndrome .” It is caused by an abnormality in cell division of chromosomes, and is also called ” trisomy 21 ” because there is an extra 21st chromosome .

It was established by the WHO in 1965 and is named after the British doctor John Langdon Down, who first described it.

It is one of the most common chromosomal abnormalities.

What is Down syndrome (Trisomy 21)? (*written with supervision of a doctor)

Down syndrome is also called Trisomy 21 because there is one more chromosome in the chromosome 21 than normal. In this a...

Characteristics of Trisomy 21 ( Down Syndrome)

Trisomy 21 (Down Syndrome) is characterized by low muscle tone and often delayed intellectual development. Development generally progresses more slowly than normal.

In addition, although this does not occur in everyone, it can also lead to other conditions such as heart disease, digestive system disease, hypothyroidism, eye diseases, and hearing loss.

Causes of Trisomy 21 (Down Syndrome)

Trisomy 21 (Down syndrome) is a congenital disorder caused by having three copies of chromosome 21.

Most cases are random and can happen to anyone. There are no specific characteristics that make a person more likely to give birth with Trisomy 21 (Down Syndrome) .

However, although the frequency is low at 5%, trisomy 21 (Down syndrome) due to “Robertsonian translocation” is hereditary. If the mother or father is a carrier of “Robertsonian translocation,” the probability of having trisomy 21 is higher than normal.

Probability of having Trisomy 21 (Down Syndrome)

Trisomy 21 (Down syndrome) is most often an accidental condition, occurring in approximately 1 in 600 to 800 births.

However, the older you are, the more likely you are to have a baby with trisomy 21 (Down syndrome). The risk of having a baby with trisomy 21 (Down syndrome) is 1 in 1,667 for mothers aged 20, 1 in 952 for mothers aged 30, and 1 in 106 for mothers aged 40.

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When is Trisomy 21 (Down Syndrome) diagnosed?

There is a chance that your baby may have Trisomy 21 (Down Syndrome) . Testing during pregnancy can help check whether or not your baby has Trisomy 21 (Down Syndrome) .

The earliest method of finding out is NIPT (non-invasive prenatal testing) . NIPT (non-invasive prenatal testing) can be taken immediately after pregnancy is confirmed by ultrasound. The test is a blood test, so there is no risk, and it has a very high sensitivity of 99%.

Although its sensitivity is lower than that of NIPT (non-invasive prenatal testing) , at 83%, the combined test can also be performed relatively early. The test involves a blood draw and an ultrasound, and can be performed between the 11th and 13th weeks of pregnancy.

Maternal serum marker testing can be done between the 15th and 17th weeks of pregnancy. This is also a blood test, but its sensitivity is 80%, which is inferior to NIPT (non-invasive prenatal testing) .

These tests are non-confirmatory, so if these tests result in doubt, confirmatory tests are usually performed.

Definitive tests include chorionic villus sampling and amniocentesis, which can reliably detect the presence or absence of trisomy 21 (Down syndrome), but have the disadvantage of carrying the risk of miscarriage or stillbirth.

Chorionic villus sampling can be performed between 11 and 14 weeks of pregnancy and has a risk of miscarriage or stillbirth of about 1%. Amniocentesis can be performed from 15 to 16 weeks of pregnancy onwards and has a risk of miscarriage of about 0.3%.

When choosing a test, be sure to consider factors such as when it is available, its accuracy, and risks.

Are there any signs of Trisomy 21 (Down Syndrome) during pregnancy?

In most cases, there are no signs that a pregnant woman can detect trisomy 21 (Down syndrome) herself during pregnancy. If you are worried about whether your baby has trisomy 21 (Down syndrome) during pregnancy , we recommend that you undergo prenatal testing.

When is the best time to get tested for Trisomy 21 (Down Syndrome)?

It is recommended that you undergo testing for Trisomy 21 (Down Syndrome) as early as possible. This will allow you enough time to discuss the results with your family after they are known. If you choose to have an abortion, the sooner the procedure is performed, the less strain it will place on the mother.

If you are thinking of getting tested, try to get it done as soon as possible.

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In some cases, an ultrasound may reveal trisomy 21 (Down syndrome).

An ultrasound examination during pregnancy may be able to detect the characteristics of a fetus with trisomy 21 (Down syndrome) . Fetuses with trisomy 21 (Down syndrome) often have swelling at the back of the neck due to poor blood flow. This swelling is called nuchal translucency (NT) and can usually be measured between the 11th and 13th weeks of pregnancy.

There are other distinctive features besides swelling at the back of the neck.

One of the most distinctive features of the face is the nose, which may be absent, thin, or have delayed growth of the nasal bone.

In addition, if physical characteristics include shorter-than-normal limb lengths, heart disease (tricuspid regurgitation/ductus venosus reflux), or a large head, it is possible that the fetus has trisomy 21 (Down syndrome) .

Because it is necessary to closely examine the facial and bodily features, 4D ultrasound is easier to detect than the 2D ultrasound used in regular prenatal checkups. If you are worried, it is a good idea to go to a maternity hospital that has 4D ultrasound.

 Probability of detecting trisomy 21 (Down syndrome) with an ultrasound

Although ultrasound can often detect the characteristics of trisomy 21 (Down syndrome) , it may not be clear depending on the position of the fetus. Also, even if findings are present, they may not be due to trisomy 21 (Down syndrome). Therefore, it is not possible to define the probability of detecting trisomy 21 (Down syndrome) .

When (at which week) can trisomy 21 (Down syndrome) be detected by ultrasound?

Trisomy 21 (Down syndrome) can generally be detected by ultrasound after the 11th week of pregnancy.

However, because ultrasound is not a definitive diagnostic method, there are cases where trisomy 21 (Down syndrome) is not detected or not detected during pregnancy even if the ultrasound is performed .

If you are worried, we recommend that you undergo NIPT (non-invasive prenatal testing) .

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Trisomy 21 (Down Syndrome) Life Expectancy

According to a study of death certificates from 2014 to 2016 in Japan, 72% of people with trisomy 21 (Down syndrome) died at age 40 or older.

As the results of treatment for complications such as congenital heart disease and congenital digestive diseases have improved, the average life expectancy has increased dramatically over the past 20 to 30 years, and the current average life expectancy of people with trisomy 21 (Down syndrome) is said to be around 60 years.

In addition to light work in facilities and workshops, many people with Trisomy 21 (Down Syndrome) work in a variety of fields, including restaurants and retail. Some people aim to become painters or musicians, while others are active as professional calligraphers, dancers, and actors.

It is important to consider how people with Trisomy 21 (Down Syndrome) can live rich lives.

If the test shows a suspicion of Trisomy 21 (Down Syndrome)

If trisomy 21 (Down syndrome) is suspected based on non-definitive tests such as NIPT (non-innovative prenatal testing) , combined testing, or maternal serum marker testing , consider undergoing definitive tests such as chorionic villus sampling or amniocentesis.

A definitive test can definitely diagnose the presence or absence of trisomy 21 (Down syndrome) . Be sure to discuss with your family in advance what to do when the diagnosis is made.

Characteristics of newborns with Trisomy 21 (Down Syndrome)

If you have not undergone chorionic villus sampling or amniocentesis, which are definitive diagnoses of trisomy 21 (Down syndrome) , you may have many concerns after birth. Newborns with trisomy 21 (Down syndrome) have characteristics such as a small head, small nose, and upturned corners of the eyes. If you notice any of these characteristics or are worried, be sure to consult your doctor immediately.

summary

We have explained the causes, tests, and characteristics of Trisomy 21 (Down Syndrome) . During pregnancy, everyone feels anxious or worried about their baby. At such times, there is an option to undergo prenatal testing.

Among these, NIPT (non-invasive prenatal testing) can be used at an early stage, has high sensitivity, and is performed by taking blood samples, so there are almost no risks. Why not consider it?

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