Source: Maternal - Fetal Medicine and Perinatology Association
Down syndrome (trisomy 21) is a genetic condition that affects lifelong development. It is not a disease. These babies are born with 3 chromosomes 21, which should be 2 in the cells of normal babies.
For this reason, they are also called trisomy 21 (See Figure). This extra chromosome can affect an individual's physical characteristics, intelligence and general development. Chromosomes contain thousands of genes, and these genes carry information that determines our characteristics (such as traits or qualities passed on to us from our family).
The extra chromosome present in Down syndrome causes delays in the child's mental and physical development. This condition is one of the most common causes of mental disability.
Although it is seen in all age groups and all socioeconomic conditions, older expectant mothers are more likely to have a baby with Down syndrome compared to younger expectant mothers (See Table).
How is Down Syndrome Diagnosed Before Birth?
Tests performed for Down syndrome in the prenatal period are divided into two groups:
Screening Tests and Diagnostic Tests. Prenatal screening tests are tests that determine the possibility of having a baby with Down syndrome. These tests do not tell whether the fetus has Down syndrome, only the probability. Diagnostic tests, on the other hand, report the final diagnosis with 100% accuracy.
Screening Tests:
First Trimester Screening Tests: 11-14 months of pregnancy. . It is done between weeks. It determines the probability by taking into account the level of two proteins in the mother's blood and some characteristics of the fetus determined by ultrasound.
Second Trimester Screening Tests: 16-18th of pregnancy. It is done between weeks. "Triple Screening Tests", which calculate the probability by looking at the levels of 3 proteins in the mother's blood, and "Quadruple Screening Tests", which calculate the probability by looking at the levels of 4 proteins in the mother's blood, constitute this group of tests.
Extracellular DNA Tests: Tests for the baby's blood in the mother's blood. These are tests that calculate probability with greater accuracy by examining DNA particles.
Diagnostic Tests:
Chorion Villus Sampling: 10-13 weeks of pregnancy. done between weeks �r. It is the determination of the chromosome structure in the cells obtained from tissue samples taken from the organ called placenta, which nourishes the baby.
Amniocentesis: 15-20 weeks of pregnancy. It is done between weeks. It is the determination of the chromosome structure in the cells in the amniotic fluid around the baby.
Cordocentesis: 18-22 weeks of pregnancy. It is done between weeks. It is the determination of the chromosome structure in the lymphocyte cells in the blood sample taken from the baby's umbilical cord.
Diagnosing in the Postpartum Period: After birth, the newborn baby has loose muscle tone, a single palm line on the palm of the hand, a flattened facial profile, eyes turned up. Diagnosis is made by taking a blood sample from the baby and performing chromosome analysis in order to make a diagnosis in the presence of findings such as slanting towards the nose, flattened nose root.
Although individuals with Down syndrome seem similar to each other and show similar behaviors, each person is different.
People with Down syndrome usually have a slightly low to moderately low IQ (a measure of intelligence) and speak more slowly than other children.
People with Down syndrome What are the Physical Characteristics of Individuals?
Some general physical characteristics of Down syndrome are as follows:
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A flat face, especially a flattened nasal bridge
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Almond-shaped upward slanting eyes
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A short neck
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Small ears
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A tongue that tends to come out of the mouth
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Small white spots in the iris (colored part) of the eye
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Small hands and feet
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A single palmar line along the palm
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Small hands and feet, sometimes sloping towards the thumb pinkish fingers
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Weak muscle tone or loose joints
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Short stature
The physical characteristics and medical problems associated with Down syndrome can vary widely from child to child. While some children need a lot of medical attention, others can survive with less support.
Although Down syndrome cannot be prevented, it can be detected before the child is born. Treating health problems that may occur with Down syndrome It can be treated and there are many resources available to help children living with this condition and their families.
Are All Down Syndrome Cases the Same?
There are three types of Down syndrome. Most of the time, the difference between the types cannot be understood without a chromosome examination. Because physical characteristics and behaviors are similar.
1. Classic Trisomy 21: About 95% of people with Down syndrome have the classic type of trisomy 21. In this type of Down syndrome, there are 3 separate copies of chromosome 21 in each cell in the body, instead of the normal 2 copies.
2. Translocation Down syndrome: This group accounts for a small percentage of people with Down syndrome (about 3%). In this type, part or all of the 21st chromosome is located or attached to another chromosome, rather than as a separate 21st chromosome.
3. Mosaic Down syndrome: This group affects about 2% of people with Down syndrome. Mosaic means mixture or combination. Some of the cells of children with mosaic Down syndrome have 3 copies of chromosome 21, but other cells typically have two copies of chromosome 21. Children with mosaic Down syndrome may have the same characteristics as other children with Down syndrome. However, fewer features of Down syndrome may be present due to the presence of cells containing a normal number of chromosomes.
Is Down Syndrome Inherited?
Most often, Down syndrome It is not hereditary. It is caused by an error in cell division during the early development of the fetus. Translocation type Down syndrome can be passed from parent to child.
However, only 3 percent of children with Down syndrome have the translocation, and only some may have passed it on from one of their parents.
It belongs to chromosome 21 in either the mother or the father. If there is a balanced translocation (a piece of chromosome 21 is attached to one of the mother's or father's other chromosomes), there is no extra genetic material from chromosome 21.
This means there are no signs or symptoms of Down syndrome, but this If the sex cell carrying the extra 21st chromosome is fertilized, it may cause an unbalanced translocation in children, causing Down syndrome.
What are the Risk Factors for Down Syndrome?
Some parents There is a higher risk of having a baby with Down syndrome. Risk factors are listed below:
Advanced maternal age: A woman's chance of having a child with Down syndrome increases with age because faulty chromosome division is more likely in older eggs.
Genetics for Down syndrome Being a translocation carrier: Both men and women can pass the genetic translocation of Down syndrome to their children.
Having a child with Down syndrome: Couples who have a child with Down syndrome and have a balanced translocation are more likely to have another child with Down syndrome. is higher. Medical geneticists can help parents evaluate the risk of having a second child with Down syndrome.
Health Problems Awaiting Babies with Down Syndrome:
As people with Down syndrome get older, may have various health problems that become more noticeable. These problems are listed below:
Heart Defects: About half (47%) of children with Down syndrome are born with some type of congenital heart defect. In 10-15% of cases, these heart problems can be life-threatening and require surgery in early infancy.
Stomach and Intestinal Problems: Some children with Down syndrome develop abnormalities in the digestive system, which can include abnormalities of the intestine, esophagus, trachea and anus. may contain. There may be an increased risk of developing digestive problems such as blockage of the gastrointestinal tract, heartburn (gastroesophageal reflux), or celiac disease.
Immune System Disorders: Due to abnormalities in their immune systems, children with Down syndrome are at risk of developing diseases such as autoimmune disorders, some types of cancer, and pneumonia. are at risk of developing infectious diseases.
Sleep Respiratory Arrest: Due to soft tissue and skeletal changes that cause airway obstruction, the risk of respiratory arrest due to obstruction is higher in children and adults with Down syndrome.
Obesity: People with Down syndrome tend to be obese compared to the general population.
Spine problems: Some people with Down syndrome may have misalignment of the top two vertebrae in the neck (atlantoaxial instability). This situation causes them to become damaged in the spinal cord due to excessive neck extension. It puts them at risk of serious injury.
Leukemia: The risk of leukemia in young children with Down syndrome increases.
Dementia: The risk of dementia increases greatly in people with Down syndrome. Signs and symptoms may begin around age 50. Having Down syndrome also increases the risk of developing Alzheimer's disease.
Other problems: Individuals with Down syndrome may also experience other health problems, such as endocrine problems, dental problems, seizures, ear infections, and hearing and vision problems. p>
Individuals with Down syndrome can continue their lives with routine medical care and treatment when necessary.
What is the Life Expectancy in Individuals with Down Syndrome?
Individuals with Down syndrome Life expectancy has increased dramatically. Today, a person with Down syndrome can live for more than 60 years, depending on the severity of their health problems.
Is it Possible to Prevent Down Syndrome?
One way to prevent Down syndrome There is no. If you are at risk of having a child with Down syndrome or have a child with Down syndrome, you may receive genetic counseling before getting pregnant.
Your medical geneticist or doctor can help you understand your likelihood of having a child with Down syndrome.
>It can also explain existing prenatal tests and help explain the pros and cons of the test.
In pregnancies diagnosed with Down syndrome, if the diagnosis is made before reaching the limit of life, the mother and father should be consulted by a medical geneticist, child health and diseases. The option of terminating the pregnancy may be offered after being informed by a team including a specialist, perinatologist or gynecologist.
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