Trisomy 21: - The most common kind of Down Syndrome accounting for around 95% of all cases. Every cell in the body has an extra chromosome 21.It is not a hereditary condition.
Mosaic Down Syndrome: - This occurs in 1 -2% of people with Down Syndrome. It can result in a milder level of intellectual disability and less obvious physical characteristics to the other forms of Down Syndrome.
Translocation Down Syndrome: - part of chromosome 21 is broken off and is then attached (translocated) onto another chromosome. This form is uncommon occurring in about 3 -4% of cases.
Genetic tests can show what type of Down Syndrome a baby has.
People unaffected by any chromosomal condition are born with 46 chromosomes in each cell (22 pairs plus 2 sex chromosomes). After conception, the fertilised egg begins to divide. Each new cell will have a matching set of chromosomes and each cell will therefore, have the same genetic code as the first cell. In Down Syndrome the chromosomes in the very early cells do not pair off correctly, and the baby begins to develop with 47 chromosomes. As a result of the extra chromosome, 1 of 3 types of Down syndrome can occur.
Due to translocation trisomy 21, it is because one of the two parents may be a balanced carrier of the translocation.
The incidence of Down Syndrome rises with increasing maternal age
Researches have established that the likelihood that a reproductive cell will contain an extra copy of chromosome 21 increases dramatically as a women ages. Therefore an older mother is more likely than a younger mother to have a baby with Down Syndrome.
Relationship Of Down Syndrome Incidence To Mothers Age
Source: Hook, E.G., Lindsjo, A. Down Syndrome in Live Births by Single Year Maternal Age
Mothers Age Incidence Down Syndrome Under 30 Less then 1 in 1,000 30 1 in 900 35 1 in 400 36 1 in 300 37 1 in 230 38 1 in 180 39 1 in 135 40 1 in 105 42 1 in 60 44 1 in 35 46 1 in 20 48 1 in 16 49 1 in 12
People with Down Syndrome look like their parents, brothers and sisters just as much as everyone else does. How ever, there are some common characteristics that tend to be shared by those with Down Syndrome. These include: -
Looser muscles and joints which make the baby seem ‘floppy’. The correct medical term for this is hypotonia.
A rather flat face with a flattened bridge in the nose
Eyes that tend to slant upwards and outwards. Those are often folds of skin between the lids in the corner of the eyes. The correct term being ‘epicanthic’ folds.
A small mouth, which seems to make the tongue stick out.
Broad hands with short fingers. The little finger may curl in a bit and there may be only a single crease across the palm
The feet may show a deep space between the first and second toe. The crease is known as a ‘scandal gap’.
A lower than average birth – weight and length.
( Routh, 2005, 17)
Down Syndrome affects, but does not determine, development and achievement in a person. People with Down Syndrome demonstrate a wide range of capabilities. What happens after birth will be far more important in shaping the outlook for a person with Down Syndrome than the occurrence of the extra chromosome at conception.
Milestone Child with Down Syndrome Other Children Holds Head Steady 3 – 9 months 1 – 4 months Sits Alone 6 – 16 months 5 – 9 months Reaches out and Grasps object 4 – 11 months 2 – 6 months Passes object from hand to hand 6 – 12 months 4 – 8 months Stands Alone 1 – 3 years 9 – 16 months Walks alone 1 – 4 years 9 – 17 months Builds a tower of two cubes 1 – 3 years 10 – 19 months Copies a circle 3 – 5 years 2 – 3 years
A child with Down Syndrome may be 2 or 3 years old before he or she says their first words, but that does not mean that they have not been communicating. All infants learn to express themselves through sounds and gestures before they can use real words, and this is true of children with down syndrome, too.
Using sign language as well as speech can really improve communication between a child with down syndrome and his or her parents.
Due to small muscles in the tongue, face and throat (more ‘floppy’) it is much more difficult for children with Down Syndrome to form words that other people can understand. In many cases a child with Down Syndrome will see a speech therapist who is trained to help develop correct speech.
(Routh, 2005, p26)
Social development and social learning are strengths right from infancy- the children enjoy and learn from social interactions with adults and peers.
Most children with down syndrome make eye contact, smile and interact by cooing and babbling from the first months of life, and show little delay in social interactive skills.
They are socially sensitive and understand the nonverbal cues to emotions, such as facial expression, tones of voice and body postures, from the first year of life.
Their good social understanding and empathy leads them to pick up on non-verbal emotional cues, such as those for anxiety or disapproval, very quickly. They are therefore sensitive to failure and may use behavioural strategies to avoid difficult situations.
Routh, K. 2005 Need to know Down’s Syndrome . Heinemann Library, Halley Court, Jordan Hill. Oxford
Down Syndrome Education International. 1996, down syndrome online < http://www.downsyndrome.org > ( updated 1 st July 2009, first accessed 24 th August 2009)
Better Health Channel. 1999, fact sheet- down Syndrome explained < http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Down_syndrome_explained > (updated February 2009, first accessed 12 th august 2009)
USA.gov. 2008, Down Syndrome < http://www.nichd.nih.gov/publications/pubs/downsyndrome.cfm#DownSyndrome > (last updated 15/08/2008, first accessed 18 th August 2009)
Government of South Australia.2009, About the Department < www.decs.sa.gov.au > (last updated 21 st January 2009, first accessed 12 th august)