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Down syndrome is a genetic difference that develops due to an extra copy of a chromosome in a chromosome pair. While healthy individuals have a total of 46 chromosomes, people with Down syndrome have 3 of the 21st chromosome. Of the chromosomes that play a role in the formation of the human body, 23 are inherited from the mother and 23 from the father. Therefore, there are two of each chromosome. It occurs when an extra chromosome is formed in the 21st chromosome pair while the baby’s cell division occurs in the womb. In other words, the total number of chromosomes in people with Down syndrome is 47. This condition, which is not a disease, is defined as a genetic difference.
Down syndrome characteristics include physical differences such as having slanted eyes, a flat nose, and a thick neck. In addition, individuals with Down syndrome often grow slower than their peers and are short in adulthood. Weight problems may occur when they do not eat a proper diet due to their slow metabolism. Before answering the question of “When does Down syndrome become apparent after birth?”, it is necessary to answer the frequently asked questions of “What is Down syndrome?” and “How does Down syndrome occur?”
Down syndrome is a genetic difference that develops before birth. The number of chromosomes in healthy individuals is 46, while it is 47 in those with Down syndrome. The question “How many chromosomes does Down syndrome have?” can be answered in this way. During the pairing of 23 chromosomes from each mother and father, 3 of the 21st chromosome are formed. It is thought that the main factor that causes this condition, which is caused by faulty cell division, is the age of the mother. The risk of developing Down syndrome is higher in pregnancies that occur after the age of 35.
There are approximately 6 million individuals with Down syndrome in the world. As in the rest of the world, one in every 800 babies in Turkey is born with Down syndrome. The reason for the extra copy of the chromosome that causes Down syndrome has not yet been determined. Frequently asked questions such as “What causes Down syndrome?” or “Is Down syndrome genetic?” can be answered in different ways depending on the type of syndrome. The extra chromosome copy is usually produced in the cell from the mother. However, it can also rarely be caused by the sperm cell from the father. Although women of all ages can give birth to a baby with Down syndrome, Down syndrome is a condition that increases in frequency as the mother ages.
There are three different types of Down syndrome: Trisomy 21, translocation and mosaic. Trisomy 21 accounts for 90% to 95% of those with Down syndrome. In the first stage of fertilization, new cells that form due to incorrect division lead to the formation of 3 chromosomes each. This occurs when chromosomes remain attached to each other as they divide, and this adhesion occurs when one side receives a single chromosome and the other side receives 2 chromosomes. Translocation is the type seen in 3% to 5% of those with Down syndrome. In translocation, a piece of chromosome 21 breaks off and attaches to a different chromosome. In this case, even though the person has 46 chromosomes, they still have 47 chromosomes genetically.
As a result, the person has the same characteristics as individuals with trisomy 21. Unlike other types, the translocation type can be hereditary. In other words, if one of the parents is a carrier, the risk of having Down syndrome with the translocation type is 33% higher in the person. The last type of Down syndrome, the mosaic type, is seen in 2% to 5% of the Down syndrome population. The mosaic type, where some cells carry 46 and some carry 47 chromosomes, is seen due to incorrect division in the later stages of fertilization. Another frequently asked question is “What are the symptoms of Down syndrome in the womb?” or “What are the symptoms of Down syndrome?”
Individuals with Down syndrome have physical and characteristic features. Common symptoms of Down syndrome include a small and flat head structure, a short and wide neck, slanted eyes, flat nose, short fingers, open big toe, curved pinky finger, and a single line on the palm. People with Down syndrome grow more slowly than healthy babies; they have loose muscle structure, hearing and vision impairment, and have difficulty learning skills such as sitting, walking, and speaking.
People with mild symptoms of down syndrome can achieve many successes with appropriate training programs. Another frequently asked question is “When does down syndrome become apparent?” Thanks to the types of tests known as down syndrome tests, the diagnosis of down syndrome can be made while the baby is in the womb. After birth, it can be understood with these types of symptoms whether the baby has down syndrome.
Down syndrome can be detected by routine screening tests during pregnancy as well as diagnostic tests. The first signs of Down syndrome are seen during an ultrasound examination and blood test performed between the 11th and 14th weeks of pregnancy. During this period, diagnosis can be made by detecting anomalies such as the baby’s height and nuchal translucency or by detecting PAPP-A and Beta hCG proteins in the blood (double test). The question “How is Down syndrome diagnosed?” can be answered in this way. However, Down syndrome can also be detected by double test, triple test, quadruple test, and fetal DNA test.
The double test, which is performed between the 11th and 14th weeks of pregnancy, is performed by taking a blood sample from the mother and examining it with an ultrasound. The mother’s blood levels of PAPP-A and Beta hCG are examined. Data such as the baby’s nuchal translucency are examined with an ultrasound.
The triple test, which is done between the 15th and 22nd weeks of pregnancy, can also be done when the double test results are not certain. The mother’s blood levels of Beta hCG, AFP (alpha feto protein) and uE3 (free estriol) are examined. The normal values of the Down syndrome test are 1/250. Data above this value is interpreted as positive. In addition, the baby’s measurements are made with ultrasonography.
The quadruple screening test, which is performed between the 15th and 22nd weeks of pregnancy, has a higher accuracy rate than other tests. During the quadruple test, Beta hCG, alpha fetoprotein (AFP), free estriol (uE3) and inhibin-A levels are examined.
Down syndrome can be detected during pregnancy by amniocentesis, cordocentesis, chorionic villus sampling, ultrasound and blood tests. Down syndrome baby movements in the womb are not noticeable by the mother-to-be. In people who do not have pregnancy follow-up, Down syndrome can be detected by the physical characteristics of the babies observed after birth.
The presence of Down syndrome is determined by double, triple or quadruple screening tests performed during pregnancy. These tests are generally performed between the 11th and 22nd weeks of pregnancy. The average lifespan of individuals with Down syndrome is 50 to 55 years. The frequently asked question, “How old does Down syndrome live?” can also be answered in this way.
The most common type of Down syndrome, defined as Trisomy 21, is not genetically transmitted. In the much rarer translocation type, genetic transmission is possible. If the mother is a carrier, the baby’s chance of being born with Down syndrome is 20%, while if the father is a carrier, this rate is between 2% and 5%.
Down syndrome is a genetic difference. In other words, since this condition is not a disease, there is no treatment for Down syndrome. However, with early supportive treatments and special training, the individual’s muscle strength and motor skills can be increased. Cognitive, social, and emotional development can be supported. All supportive treatments also help develop the intelligence level of the person with Down syndrome. Another frequently asked question is “Does Down syndrome recur?”
The probability of having a baby with Down syndrome in the second pregnancy of parents with a child with Down syndrome is 1%. This rate is 0.1% for expectant mothers who have not given birth to a baby with Down syndrome before.
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