About Down Syndrome
Mother's AgeThe chance of having a baby with Down Syndrome increases significantly with age; for example, between 20 and 24 years of age, the chance of conceiving a child with Down syndrome is one in 1,450, while at age 45 this probability increases to one in 32.
Down Syndrome is a chromosomal disorder that occurs in approximately 1 in 900 births in Canada. Although it is not known for sure, it is possible that an error in cell division causes this extra chromosome. This extra chromosome material is present at conception, either from the father’s sperm or the mother’s egg, each of which contributes 23 chromosomes. The extra chromosomal material can be contributed either by the mother or the father.
A person with Down Syndrome has 47 chromosomes in each cell instead of 46. It is important to know that nothing the mother does during pregnancy could cause this to happen.
Two to three per cent of people with Down syndrome have a translocation pattern. In translocation, during cell division, a part of the number 21 chromosome breaks off and attaches itself to another chromosome, usually the number 14 chromosome. About two-thirds of these translocations occur spontaneously while the rest are inherited from a parent. If the chromosome test shows a translocation, it is recommended that the parents have their own chromosomes analysed as the chance of having other children with Down syndrome may increase significantly.
Approximately two per cent of people with Down syndrome have mosaicism. In this case, a faulty cell division occurs in one of the early cell divisions after conception, resulting in some cells having 46 chromosomes and some having 47. The percentage of cells with 47 chromosomes instead of 46 varies from person to person.
Characteristics of People with Down Syndrome
There are several physical characteristics that are more common for babies with Down syndrome. They may include chubby cheeks, large, round eyes, larger tongue, smaller limbs and smaller body frame.
Newborns with Down syndrome look like babies who do not have Down syndrome. Babies and children with Down syndrome look like other members of their family.