Chromosomes And How They Work
To understand Down Syndrome, you first have to learn what chromosomes are. Chromosomes exist inside the bodys cells. They are codes that tell the body how to grow. These codes control everything from the color of a persons hair, to whether they are a boy or a girl.
Chromosomes start working before a baby is even born, as it develops in the womb. They are there from the time a human is composed of only one cell. As the baby grows, it is composed of many, many more cells, but inside every cell exists the same set of chromosomes.
In every cell, a person has 46 chromosomes . Everyone has their own unique code. Thats why we all look different. The only people who have the same code are identical twins, and that is why they look the same.
All of us generally receive 23 chromosomes from our mother and 23 from our father. Each of them can be identified. They have names like Chromosome 1, Chromosome 2, Chromosome 3, all the way to Chromosome 23. Generally, we all have two of each chromosome, after receiving one of each from each parent. This also explains why you might look a little like one or both of your parents.
Genetic Screening For Down Syndrome
The American College of Obstetrics and Gynecology recommends that all expecting women be offered prenatal genetic screening. It is not compulsory and can be refused, but it remains an option for any age. Previously, only women over 35 were offered screening.
First Trimester screening uses a combination of factors to assess your baby’s risk for certain chromosomal abnormalities. The screen is generally understood to check for Trisomy 21 , but it also checks for another abnormality called Trisomy 18.
A screening test provides you with a chance of having a child with a chromosomal abnormality. It will not tell you if your baby has or does not have a chromosomal abnormality. It is important to understand that screening is not diagnosis. It’s possible to be considered high risk and have a completely normal baby, and it’s possible to be considered low risk and have a baby with an abnormality.
When Was Down Syndrome Discovered
For centuries, people with Down syndrome have been alluded to in art, literature and science. It wasnt until the late nineteenth century, however, that John Langdon Down, an English physician, published an accurate description of a person with Down syndrome. It was this scholarly work, published in 1866, that earned Down the recognition as the father of the syndrome. Although other people had previously recognized the characteristics of the syndrome, it was Down who described the condition as a distinct and separate entity.
In recent history, advances in medicine and science have enabled researchers to investigate the characteristics of people with Down syndrome. In 1959, the French physician Jérôme Lejeune identified Down syndrome as a chromosomal condition. Instead of the usual 46 chromosomes present in each cell, Lejeune observed 47 in the cells of individuals with Down syndrome. It was later determined that an extra partial or whole copy of chromosome 21 results in the characteristics associated with Down syndrome. In the year 2000, an international team of scientists successfully identified and catalogued each of the approximately 329 genes on chromosome 21. This accomplishment opened the door to great advances in Down syndrome research.
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Intellectual Down Syndrome Characteristics
Down syndrome affects kids’ ability to learn in different ways. Most children have mild to moderate intellectual impairment, and they tend to acquire new skills slowly, explains Kenneth Rosenbaum, M.D., founder of the division of genetics and metabolism and co-director of the Down Syndrome Clinic at Children’s National Medical Center in Washington, D.C. Speech and language skills may take longer than normal to form. Developmental delays could also cause impulsive behavior, a short attention span, stubbornness, and poor judgement.
Because the first years of life are so critical for a child’s future development, all babies born with Down syndrome are eligible for free early intervention services via the federally mandated Individuals with Disabilities Education Act . These include physical therapy speech-language therapy and occupational therapy .
Dr. Rosenbaum adds that some children with Down syndrome enroll in special education classesbut others thrive in mainstream classrooms. Your child will keep learning throughout their life with proper support and education.
How Is Down’s Syndrome Diagnosed
Down’s syndrome can be diagnosed before birth or after birth .
Down’s syndrome may be suspected shortly after birth because of the typical features that a baby with Down’s syndrome may have. Diagnosis is confirmed by genetic tests to look at the appearance and number of chromosomes of the baby. This is essentially their genetic make-up. It involves the baby having a blood test. The chromosomes in their blood can then be examined to look for an extra chromosome 21.
The rest of this leaflet concentrates on screening for Down’s syndrome and the diagnosis of Down’s syndrome during pregnancy, before the baby is born.
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Is Down Syndrome Genetic
In most cases, Down syndrome is not inherited and does not run in families. Though Down syndrome comes from the genes themselves, this is generally due to errors between a sperm and an egg, when the genetic information that forms a child first combines and copies.
Down syndrome can have links to genetics. There may be some links between parents of a person with translocation Down syndrome and their likelihood to have more children with Down syndrome in some cases.
The Genetic and Rare Diseases Information Center notes that in parents of a child with Down syndrome due to translocation, there may be an increased chance of Down syndrome in future pregnancies if one of the parents has a genetic rearrangement called a balanced translocation. However, this does not occur in every case of translocation Down syndrome.
Individuals with Down syndrome commonly have distinct physical features, unique health issues, and changes in cognitive development.
How Down Syndrome Is Diagnosed
Down syndrome can be diagnosed almost as soon as a baby is born, based on distinctive physical characteristics that prompt immediate testing. Down syndrome can also be diagnosed, or at least suspected, based on any of several prenatal tests including a nuchal translucency screening, sonogram, quadruple screen, or other blood tests. Here is how Down syndrome is diagnosed in both scenarios.
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What Is Down’s Syndrome
Down’s syndrome is a genetic chromosome problem that some people are born with. A person with Down’s syndrome can usually be recognised by their typical features. It can also cause learning disability and there are certain medical problems that someone with Down’s syndrome has an increased risk of developing. These include a congenital heart defect , vision problems or growth problems. There is no cure for Down’s syndrome. It will affect someone throughout their life.
Someone with Down’s syndrome has an extra copy of chromosome 21 in the cells of their body. This is known as trisomy 21 . Because there is an extra chromosome 21, there is extra genetic material in the body. This causes the typical features of Down’s syndrome. See the separate leaflet called Down’s Syndrome for more details.
What Is The Difference Between A Screening Test And A Diagnostic Test
A screening test will help identify the possibility of Down syndrome. Screening tests do not provide conclusive answers, but rather, they provide an indication of the likelihood of the baby having Down syndrome. An abnormal test result does not mean that your baby has Down syndrome.
The goal with a screening test is to estimate the risk of the baby having Down syndrome. If the screening test is positive and the risk for Down syndrome exists, further testing may be recommended. Diagnostic tests can identify Down syndrome before the baby is born.
In the January issue of Obstetrics & Gynecology, the American College of Obstetricians and Gynecologists released guidelines recommending screening for Down syndrome to all pregnant women during their first trimester.
Diagnostic tests tend to be more expensive and have a degree of risk screening tests are quick and easy to do. However, screening tests have a greater chance of being wrong there are false-positive and false-negatives .
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Diagnostic Tests For Down’s Syndrome
The two main tests that are used to diagnose Down’s syndrome before birth are amniocentesis and chorionic villus sampling . In both tests samples are taken from the inside of your womb with a needle usually passed through your tummy. There are pros and cons to both tests:
- Both tests carry a small risk of miscarriage.
- Both tests give a definite answer as to whether your baby has one of these syndromes.
- CVS can be done earlier in pregnancy than amniocentesis.
Both tests are discussed further in separate leaflets. See the separate leaflets called Amniocentesis and Chorionic Villus Sampling .
What Causes Down Syndrome In A Child
When a baby is conceived, a normal egg cell and normal sperm cell start with 46 chromosomes. The egg and sperm cells then divide in half. The egg and sperm cells then have 23 chromosomes each. When a sperm with 23 chromosomes fertilizes an egg with 23 chromosomes, the baby will then have a complete set of 46 chromosomes. Half are from the father and half are from the mother.
But sometimes an error occurs when the 46 chromosomes are being divided in half. An egg or sperm cell may keep both copies of chromosome number 21, instead of just 1 copy. If this egg or sperm is fertilized, then the baby will have 3 copies of chromosome number 21. This is called trisomy 21.
Sometimes the extra number 21 chromosome or part of it is attached to another chromosome in the egg or sperm. This may cause translocation Down syndrome. This is the only form of Down syndrome that may be inherited from a parent.
A rare form is called mosaic trisomy 21. This is when an error in cell division happens after the egg is fertilized. People with this syndrome have both normal cells and some cells with an extra chromosome number 21.
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Love And Learning: A Language And Reading Development Tool For Babies And Toddlers
Love and Learning, which was developed by Joe and Susan Kotlinski, is an innovative technique that teaches both reading and language skills to babies and toddlers.
The couple created the program after the birth of their daughter who was diagnosed with Down syndrome. The method uses a mixture of special audio CDs, DVDs, computer programs and books that includes a fair amount of parental involvement.
Whats So Special About The Technique?
Its an original piece of work, presenting letters and words in a clear way that helps Down syndrome children put their attention on each individual sound of a word.
The audio CD is used during playtime, bedtime or naptime so the child can hear the words in a slow, concise way. They are phonetically and visually repeated in a focused way.
Special books also present the same words/letters, and when used for several minutes on a daily basis, it reinforces the audio CD and DVD.
It also helps to give the child and parent some reading time together.
Every DVD offers a presentation to parents on how best to use the method to help their childs individual needs. Love and Learning provides a method that is focused on their success to boost their self-esteem and sound learning principles.
To learn more, you can check out www.loveandlearning.com.
How Add-A-Bands Can Help Children With Down Syndrome
They can also be used to reduce the excessive leg widening, especially for children who suffer from nerve damage paralysis or muscle weakness.
Who Is At Risk Of A Down Syndrome Pregnancy
- The children of women who fall pregnant after the age of 35 have up to a 1 in 250 chance of being born with Down syndrome. The older the woman is when she becomes pregnant, the higher the risk of a Down syndrome pregnancy.
- Women who have already given birth to a child with Down syndrome have an increased chance of having another child with the condition from any subsequent pregnancies.
- Those with a family history of Down syndrome, for instance in brothers, sisters or other blood related relations, are at risk.
- Women who have undergone an ultrasound examination that produced signifiers associated with Down syndrome are also at risk.
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Characteristics Of Infants Born With Down Syndrome
Children with Down syndrome all have the following similar characteristics: A flat head, an abnormal facial structure including bulbous eyes that are far apart, a flat nose, low set ears, a small mouth, and an enlarged tongue. They are shorter than average, with short legs, hands and fingers, while they lack the middle bone in their little fingers and have wide palms and feet. Their muscles are soft and limp, being unable to contract properly and they develop slowly, both physically and mentally. They have low IQ score or mental disabilities, while many of them also suffer from various other health disorders, such as congenital heart defects or intestinal obstruction.
Nuchal Translucency Ultrasound Screening
This specialized ultrasound, which is performed at 11 to 13 weeks, measures the thickness of an area of tissue at the back of a fetus’s neck called the nuchal fold. Though this test is recommended for all pregnant women, this is a difficult measurement to obtain and only someone who has been specifically trained and certified to perform this screening can do it.
In general, a measurement under 3 millimeters is considered normal and one that’s over 3 mm is considered abnormal . In the latter case, it will be important to meet with a genetic counselor to discuss your screening results, what they mean, and your diagnostic testing options such as chorionic villi sampling or amniocentesis .
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Can You Find Out During Pregnancy If Your Baby Has Down Syndrome
Yes. Health care providers offer testing for Down syndrome to all pregnant women as part of regular prenatal care . You can decide if you want to have these tests. Talk to your health care provider or a genetic counselor about testing for Down syndrome.
If you or your partner has a family history of Down syndrome, tell your health care provider or genetic counselor. Family history means that someone in either of your families has the condition. Use our family health history form to help you find out if certain health conditions run in your families.
There are two kinds of prenatal tests to check for Down syndrome:
What Diagnostic Tests Are Used For Down Syndrome
During a diagnostic test, your provider uses a needle to take a sample of your babys blood, amniotic fluid or tissue for testing. There is a small risk of miscarriage with these diagnostic tests. Miscarriage is when a baby dies in the womb before 20 weeks of pregnancy.
Diagnostic tests for Down syndrome include:
- Chorionic villus sampling . This test checks tissue from the placenta to see if your baby has a genetic condition, like Down syndrome. You can get CVS at 10 to 13 weeks of pregnancy.
- Amniocentesis . This test takes some amniotic fluid from around your baby in the uterus to check for birth defects and genetic conditions in your baby. You can get this test at 15 to 20 weeks of pregnancy.
- Percutaneous umbilical cord sampling . This test takes a small amount of your babys blood from the umbilical cord to check for chromosome defects. You can get this test between 18 and 22 weeks of pregnancy. There are greater risks with PUBS than with amnio or CVS, so you only get this test if other tests are unclear and you want to confirm whether or not your baby has Down syndrome.
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What If I Decide Not To Have This Test
If you choose not to have the screening test for Down’s syndrome, Edwards’ syndrome or Patau’s syndrome, you can still choose to have other tests, such as a 12-week scan.
If you choose not to have the screening test for these conditions, it’s important to understand that if you have a scan at any point during your pregnancy, it could pick up physical conditions.
The person scanning you will always tell you if any conditions are found.
What Is Down Syndrome In Children
Down syndrome is a genetic disorder. It is also called trisomy 21. It includes certain birth defects, learning problems, and facial features. A child with Down syndrome also may have heart defects and problems with vision and hearing. How severe or mild these problems are varies from child to child.
Down syndrome is one of the most common genetic birth defects. It affects about 1 in 800 babies. Adults with Down syndrome may live about 60 years, but this can vary.
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