What is Down syndrome? Down syndrome is a genetic condition in which a person has 47 chromosomes instead of the usual 46. This disorder causes mental retardation and other problems. Down syndrome ranges in severity, so developmental problems may range from mild to serious.
Causes of Down syndrome There are 3 possible abnormalities which all result in extra genetic material from chromosome 21,which causes Down syndrome. 1 2 Trisomy 21 Mosaic Down syndrome 3
More than 90 percent of cases with Down syndrome are caused by Trisomy 21.
With Trisomy 21 there are 3 copies of chromosome 21, instead of the usual 2 copies.
Translocation Down syndrome
rare form of Down syndrome
With Mosaic Down syndrome some cells have an extra copy of chromosome 21, but not all.
Mosaic Down syndrome is caused by abnormal cell division after fertilization.
occurs when part of a chromosome 21becomes attached onto another chromosome, before or at conception.
Children with Translocation have the usual 2 copies of chromosome 21, but have additional material from chromosome 21 stuck to the translocated chromosome.
MOST cases of Down syndrome are NOT inherited.
Common physical signs of Down syndrome Individuals with Down syndrome have a widely recognized appearance. Common physical signs include:
upward slanting eyes
wide, short hands with short fingers
separated joints between the bones of the skull
decreased muscle tone at birth
Risk Factors A woman’s chance of giving birth to a child with Down syndrome increases with age. Advance Maternal Aging
Age 35 = 1 in 385 chance
Age 40 = 1 in 106 chance
Age 45 = 1 in 30 chance
Women who already have a child with Down syndrome typically have a 1 % chance of having another child with Down syndrome. Parents who are carriers of the translocation for Down syndrome can pass the genetic translocation onto their children.
Statistics about Down syndrome
about 1-in-800 risk overall for all births
340,000 people in USA
88% of cases arise from mother's chromosome 21; 8% from father's chromosome 21; 2% from mitotic errors after fusion
66-88% of down patients have some level of hearing loss in at least one ear
40 to 50% of children with Down syndrome have congenital heart defects in the US
Tests and Diagnosis The most efficient two step screening is done during the 11th week and 14th week of pregnancy. First the doctor does an ultrasound to get results, those results are then paired with blood tests. “When this two-step screening is done during the 11th week of pregnancy, researchers say it can identify 87 percent of babies with Down syndrome.” If a screening test indicates a high chance of Down syndrome, more tests are done to see if the baby actually had Down syndrome.
Tests for positive results If your tests came back positive or are at a high risk for Down syndrome, you can have further testing. Amniocentesis
A sample of amniotic fluid is withdrawn from the mother’s fetus, this sample is used to analyze the chromosomes of the fetus.
The chance of miscarriage from taking this test is 1 in 200.
Chorionic villus sampling (CVS)
To analyze the fetal chromosomes, cells are taken from the mother’s placenta.
The risk for miscarriage by taking this test is 1 in 100.
Percutaneous umbilical blood sampling (PUBS)
To exam for chromosomal defects, blood is taken from the vein in the umbilical cord.
This test has a greater risk for miscarriage than both Amniocentesis and CVS.
Test usually is only done if completely necessary.
Complications with Down Syndrome Children with Down syndrome are more likely to have complications. There is a range listed below. Heart Defects Leukemia Infectious Diseases Dementia
Famous people with Down syndrome Chris Burke Jane Cameron Sujeet Desai Bernadette Resha Never set limitations for yourself.
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