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Down Syndrome Down Syndrome
Down syndrome is a genetic disorder also called trisomy 21. It occurs in approximately 1 out of every 800 births and is the... Down Syndrome

by Kimberley Allen R.N.

Down syndrome is a genetic disorder also called trisomy 21.  It occurs in approximately 1 out of every 800 births and is the most common cause of cognitive impairment.  Down Syndrome occurs in both males and females as well as all ethnic groups.
We all receive 23 chromosomes from each parent at conception.  Down syndrome occurs when a person inherits two chromosomes 21 from the mother and one chromsome 21 from the father, this makes three chromosomes 21 thus the name trisomy 21.  There are a small percent of people that don’t inherit and entire third chromosome 21 only a few of the genes from a third chromosome 21 that attach to another chromosome.  This type of down syndrome is known as translocation.

Down syndrome is caused by a defect in the chromosomes.

Another type of down syndrome that occurs in a small percentage of people is known as Mosaic down Syndrome.  This occurs when a person inherits additional genes from chromosome 21, however not all cell are affected.  For example, a person may inherit extra genes from chromosome 21 that affects only the muscle cells or only nerve cells etc.
The risk of conceiving a child with Down Syndrome increases as the maternal age at conception increases.  For example a woman 25years has a 1 in 1,250 chance of having a child with down syndrome, but a woman 45years has a 1 in 30 chance of having a child with down syndrome. Other risk factors include parents that have down syndrome especially women have a 50% risk of having a child with down syndrome.
Children with down syndrome usually all have similar physical characteristics including a flat face with an upward slant to both
eyes, small ears and a large tongue.  Poor muscle tone is also  common in children with down syndrome.  Most babies with down syndrome appear “floppy” and though they may have difficulty reaching the developmental milestones like sitting, crawling, and walking they are usually able to accomplish them, just a little later than other babies.
Mild to moderate learning disabilities are also common in children with down syndrome.  Children with down syndrome can still learn and develop the skills need to function in life, but at a slower pace. There are some children with severe down syndrome that will require 24hour care their whole life.  I know of one girl that is 28yrs of age, however she only has language and functioning skill of a 9yr old.
Many down syndrom children also have othe medical problems that require extra medical attention, like heart problems.  Approximately 50% of all children born with down syndrome will also have a congenital heart defect, they also have an increased risk of developing pulmonary hypertension.  For these reasons all children born with down syndrome need to be examined by a pediatric cardiologist.  There is also a significant number of children with down syndrome that have problems with vision and hearing.  There are other health issues that are more prevelent in children with down syndrome including and increased suseptibility to infection and an increased risk of childhood leukemia.
Down syndrome can be diagnosed during pregnacy.  There are two methods for prenatal testing, screening testskwhich estimate the risk that the fetus may have down syndrom and diagnostic tests which can tell whether or not the fetus actually has down syndrome.

Kimberly Allen is a registered nurse with an AND in nursing. She has worked in ACF, LCF and psychiatric facilities, although she spent most of her career as a home health expert. She is now a regular contributor to, dispensing advice and knowledge about medical issues and questions. You can reach her with any comments or questions at