Extra fluid in this region could indicate a genetic problem. Rarely, screening tests can give an abnormal result even when there is nothing wrong with the baby. Sometimes, the test results are normal and yet they miss a problem that does exist. Diagnostic tests are usually performed after a positive screening test in order to confirm a Down syndrome diagnosis.
Types of diagnostic tests include:. Many people with Down syndrome have the common facial features and no other major birth defects. However, some people with Down syndrome might have one or more major birth defects or other medical problems. Some of the more common health problems among children with Down syndrome are listed below. Down syndrome is a lifelong condition. They don't make a diagnosis. A diagnostic test is more invasive and risky. But it generally can find the disorder.
The screening ultrasound looks at the amount of amniotic fluid present. Extra fluid means there is a problem. These tests look at various levels of certain substances such as alpha-fetoprotein, human chorionic gonadotropin, estriol to determine risk.
Fetal ultrasound during pregnancy can also show the possibility of Down syndrome. Problems from Down syndrome may not be seen with ultrasound. Diagnostic tests are done by looking at cells in the amniotic fluid or from the placenta. These tests include:. Chorionic villus sampling. This test examines cells from the placenta. This tests the fluid from the sac surrounding the baby amniotic fluid.
Percutaneous umbilical blood sampling. This tests blood from the umbilical cord. All 3 of these tests look for characteristic changes in the chromosomes that occur in a Down syndrome diagnosis. After birth, your baby may be diagnosed with a physical exam. The healthcare provider may also take a blood sample.
This is checked in a lab to find the extra chromosome. There is no cure for Down syndrome. But a child with Down syndrome may need treatment for problems such as:. Heart defects. About half of babies with Down syndrome have heart defects. Some defects are minor. These can be treated with medicines or they will fix themselves on their own. Others may need surgery. All babies with Down syndrome should have an echocardiogram heart ultrasound and be looked at by a pediatric cardiologist.
This exam and test should be done shortly after birth. This is so that any heart defects can be found and treated correctly.
Intestinal problems. Some babies with Down syndrome are born with intestinal problems that need surgery. Vision problems. Common problems include crossed eyes, nearsightedness or farsightedness, and cataracts. Most eyesight problems can be made better with eyeglasses, surgery, or other treatments. Your child should see an eye doctor pediatric ophthalmologist before they turn 1 year old. In Down syndrome, there is an additional copy of chromosome 21, resulting in three copies instead of the normal two copies.
Down syndrome is a genetic disorder caused when abnormal cell division results in an extra full or partial copy of chromosome This extra genetic material causes the developmental changes and physical features of Down syndrome. Down syndrome varies in severity among individuals, causing lifelong intellectual disability and developmental delays. It's the most common genetic chromosomal disorder and cause of learning disabilities in children.
It also commonly causes other medical abnormalities, including heart and gastrointestinal disorders. Better understanding of Down syndrome and early interventions can greatly increase the quality of life for children and adults with this disorder and help them live fulfilling lives. Each person with Down syndrome is an individual — intellectual and developmental problems may be mild, moderate or severe.
Some people are healthy while others have significant health problems such as serious heart defects. Children and adults with Down syndrome have distinct facial features. Though not all people with Down syndrome have the same features, some of the more common features include:.
Infants with Down syndrome may be average size, but typically they grow slowly and remain shorter than other children the same age. Most children with Down syndrome have mild to moderate cognitive impairment. Language is delayed, and both short and long-term memory is affected. Children with Down syndrome usually are diagnosed before or at birth. However, if you have any questions regarding your pregnancy or your child's growth and development, talk with your doctor.
Human cells normally contain 23 pairs of chromosomes. One chromosome in each pair comes from your father, the other from your mother.
Down syndrome results when abnormal cell division involving chromosome 21 occurs. These cell division abnormalities result in an extra partial or full chromosome This extra genetic material is responsible for the characteristic features and developmental problems of Down syndrome.
The genes are made of DNA deoxyribonucleic acid. The arrangement of chemicals in the DNA is different for every gene. These chemical instructions tell the body what components to make, and how, when and in what quantity to make them, in order to ensure normal working of the body.
There are also long stretches of DNA, the precise role of which is still a mystery. Chromosomes The genes are grouped together in long, thin, thread-like structures called chromosomes. Thus chromosomes carry our genetic information. There are 46 chromosomes in 23 pairs in all body cells except the sperm and egg cells.
Each pair of chromosomes has different genes. One chromosome of each pair comes from the mother and one from the father. A person's characteristics are determined by the interaction of the copies of the genes from each parent. The chromosome pairs are numbered according to size. Chromosome 1 is the largest. Each chromosome has a long arm and a short arm. The 23rd pair are the sex chromosomes which are called the X and Y chromosomes. Girls have two X chromosomes and boys have an X and a Y.
The sex chromosomes are different from the others. In chromosome tests, the chromosomes usually from blood cells are stained with dye. Each pair has a different staining pattern. When seen down a microscope the chromosomes lie in a haphazard manner, but when they are photographed, cut out and arranged in pairs, a picture of an individual's chromosomes known as a karyotype is obtained.
The genes, thousands on each chromosome, are spaced along the length of the DNA molecule, in a definite order. Apart from the X and Y chromosomes, the order of the genes on one chromosome exactly matches the order on the other chromosome of the same pair and on chromosomes of the same number in everyone else.
In general, there are only two copies of each gene and in all people they are always on the same chromosome pair. The two copies of each gene may not be identical. Any changes may be small "misprints" or bigger alterations, with a corresponding effect of the "readability" of the instructions.
When this happens, variation occurs between people - this variation is sometimes advantageous, sometimes neutral and sometimes unhelpful. Often a mistake in the one copy of a gene can be "cancelled out" when there is no mistake is the other copy of the same gene. Geneticists believe that everyone carries a number of defective genes which are partnered by a normal copy which "cancels" the defect.
They also believe we all carry a number of genes with small variations which are not cancelled out, and which account for some of the differences in appearance or health among people in the general population. Ordinary cell division The body grows by making new cells. New cells are made by one existing cell dividing into two. In order to work, each new cell needs a set of 46 chromosomes.
Before a cell divides an exact copy of each chromosome is made, creating a complete new set. The two sets of chromosomes move to opposite ends of the cell. The cell then divides across the middle producing two new cells, each with 46 chromosomes.
This type of cell division is known as mitosis. Eggs and Sperm Eggs and sperm are different from all other cells in that they contain only a single set of 23 chromosomes. This means that when the egg and sperm come together at fertilisation, the usual number of 46 is restored, ready for the baby's development.
There is a special type of cell division used only in the making of eggs and sperm. This special type of cell division is called meiosis. Meiosis involves two rounds of cell division. The first round is very specialised; it is called reduction division, because it reduces the number of chromosomes to The second meiotic division is similar to ordinary cell division mitosis.
Men make millions of fresh sperm, all the time, from puberty onwards. It is quite different in women. Long before birth, the female embryo has already started making the cells which will form her eggs when she is a mature woman. After puberty, a woman's ovaries release one egg or occasionally more per month until menopause. All eggs made by the mother will contain one copy each not a pair of chromosomes , and an X chromosome.
All sperm made by the father will contain one copy each not a pair of chromosomes and either an X or a Y chromosome. If an X-carrying sperm fertilises the egg the baby will be a girl, whilst if a Y-carrying sperm fertilises the egg the baby will be a boy. When a chromosome egg is fertilised by a chromosome sperm, the first cell of a 46 chromosome embryo, fetus and baby is made. All that baby's cells will have the same 46 chromosomes which were in the original fertilised egg. Overview Down's syndrome occurs in babies born with extra chromosome 21 material in their cells.
Down's syndrome is also known as trisomy Trisomy 21 means there are 3 tri copies of chromosome somy Down's syndrome therefore arises from a change in gene quantity rather than gene quality. We do no know exactly why Down's syndrome occurs.
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