Causes of Down syndrome, a genetic chromosomal abnormality in babies

All parents want their baby to be born safely and healthily into the world. Unfortunately, there are some babies who have birth defects that make their bodies less than perfect. One of the conditions for birth defects in babies is Down syndrome. So, what exactly causes Down syndrome or Down syndrome?

What causes Down syndrome?

Down syndrome is the most common genetic chromosome disorder. Broadly speaking, the cause of Down syndrome or Down syndrome is because the baby has an excess number of chromosomes while in the womb.

This Down syndrome condition should not be underestimated because it can cause children to have learning difficulties.

The incidence rate of Down syndrome or Down syndrome worldwide is estimated at 1 in 700 of the total birth rate.

In other words, there are approximately eight million children who have Down syndrome. Meanwhile, based on the Data and Information Center of the Indonesian Ministry of Health, Down syndrome cases in Indonesia tend to increase.

According to the results of Basic Health Research (Riskesdas), there are about 0.12 percent of Down syndrome cases in children aged 24-59 months.

This result increased to 0.13 percent in 2013 to change to 0.21 percent in 2018. It should be noted that Down syndrome is generally not a hereditary disease.

As previously mentioned, the presence of genetic disorders when the unborn baby has an additional chromosome 21 is the cause of Down syndrome or Down syndrome.

The additional chromoson 21 can occur in full or only partial copies, whether it is formed during the development of an egg, the formation of a sperm cell, or an embryo.

In more detail, there are normally 46 chromosomes in human cells and each pair of chromosomes is formed from the father and mother.

If when abnormal cell division also involves chromosome 21, this is where Down syndrome or Down syndrome occurs. Abnormalities in the process of cell division which then results in chromosome 21 or extra partial chromosomes.

Genetic variations that cause Down syndrome

Launching from the Mayo Clinic page, there are several genetic variations that can cause Down syndrome:

Causes of Down Syndrome due to trisomy 21

There are about 95 percent of the causes of Down syndrome due to trisomy 21. If a child with Down syndrome usually has two copies of the chromosome, this is different from trisomy 21 cases.

A child with trisomy 21 has three copies of chromosome 21 in all of their cells. This condition can occur due to abnormal cell division during the development of sperm or egg cells.

As an illustration, the chromosomes line up neatly to produce eggs or sperm in a process called meiosis.

However, trisomy 21 had an unfavorable effect. Instead of giving one chromosome, two chromosomes 21 are given.

So later, after being fertilized, the egg, which should have only two chromosomes, actually has a total of three chromosomes. This is one of the causes of Down syndrome.

Mosaic Down Syndrome (Mosaic Down syndrome)

When compared with the two types of genetic variations that cause Down syndrome or Down syndrome previously described, this type of mosaic is the rarest.

Mosaic Down syndrome is the cause of Down syndrome which occurs when a person has only a few cells with an extra copy of chromosome 21.

The exact cause of mosaic Down syndrome is different from the previous two types and is not yet known.

That is why, the traits or characteristics of a child with mosaic Down syndrome are more difficult to predict, unlike the two previous types.

These traits or characteristics may appear less clear depending on which cells and how many cells have the additional chromosome 21.

Translocation Down Syndrome (Translocation Down syndrome)

Down translocation syndrome is a condition when a part of chromosome 21 attaches to another chromosome before or when fertilization occurs.

A child with Down's translocation syndrome has the usual two copies of chromosome 21. However, the child also has additional genetic material from chromosome 21 attached to the other chromosome.

The cause of this type of Down syndrome is due to abnormal cell division, either before or after the fertilization process is complete.

In contrast to other types of Down syndrome causes, Down's translocation syndrome is a type that can sometimes be inherited from parents or genetics.

Even so, only about 3-4 percent of cases of translocated Down syndrome actually get it from one parent.

If the translocation of Down syndrome passes to the child, this means that the father or mother has some genetic material for chromosome 21 rearranged on another chromosome.

However, there is no additional genetic material on chromosome 21 in cases of translocation Down syndrome. This means that the father or mother does not actually have signs or symptoms of Down syndrome.

However, the father or mother can pass it on to the child because it carries this genetic material, which causes the child to experience Down syndrome.

This condition causes additional genetic material from chromosome 21. The risk of reducing translocation Down syndrome depends on the sex of the parent carrying chromosome 21, which is as follows:

If father is a carrier agent (carrier), the risk of Down syndrome is about 3%
If the mother is a carrier agent (carrier), the risk of Down syndrome ranges from 10-15%

A bearer (carrier) may show no signs or symptoms of Down syndrome, but it can reduce the translocation process to the fetus.

What are the risk factors for having a Down syndrome baby?

Some theories suggest that Down syndrome is triggered by how well the mother's body processes folic acid.

However, many also oppose this theory, because there is a lot of confusion regarding the factors that influence the occurrence of Down syndrome.

This is explained by Kenneth Rosenbaum, M.D, head of the division of genetics and metabolism and deputy director of the Down Syndrome Clinic at Children's National Medical Center in Washington, D.C.

There are certain conditions that can increase your risk of having a baby with Down syndrome. These are called risk factors.

Here are some risk factors for Down syndrome or Down syndrome:

1. Maternal age at pregnancy

The mother's age at pregnancy is not the cause of Down syndrome, but it is a risk factor. Down syndrome can occur at any age when the mother is pregnant.

However, the chances of developing Down syndrome will increase with age.

The risk of carrying a baby with genetic problems, including Down syndrome, is believed to increase when a woman reaches 35 years of age or older while pregnant.

This is because the eggs of women who are older are at greater risk for improper chromosome division.

Even so, it does not rule out the possibility of children with Down syndrome being born to women aged less than 35 years because of the increase in pregnancy and birth rates at a young age.

Women who are 25 years old at the time of pregnancy have a 1 in 1200 risk of giving birth to a baby with Down syndrome.

Meanwhile, women who are 35 years old at the time of pregnancy have a risk of up to 1 in 350 people. Likewise, in pregnant women aged 49 years, the risk of developing Down's syndrome increases to 1 in 10 people.

They found that the uterus of women approaching menopausal age and the risk of infertility also increased.

In addition, the ability to select defective embryos decreases and increases the risk that the unborn child will experience complete developmental decline.

2. Have had a Down syndrome baby before

Women who have had a baby with Down syndrome have a higher risk of having a future baby who also has Down syndrome.

This also applies to parents who have translocation Down syndrome so that they are at risk of affecting the baby.

3. Number of siblings and distance of birth

The risk of a baby born with Down syndrome also depends on how many siblings are and how large the age gap is between the youngest child and the baby.

This is explained in the research of Markus Neuhäuser and Sven Krackow, of the Institute of Medical Informatics, Biometry and Epidemiology at University Hospital Essen.

As previously explained, the risk of having a baby with Down syndrome is higher in women who are pregnant for the first time at an older age.

This risk will also increase the further the distance between pregnancies is.