Down syndrome also called "mongolism" is a chromosomal variation that consists of an extra chromosome twenty-one. It usually causes delays in physical and intellectual development. Down syndrome can be determined during pregnancy, however the degree of Down syndrome cannot be determined until the child is born. Some individuals with Down syndrome have medical problems including heart defects (33%), vision and hearing impairment, vertebral instability, and thyroid problems. However there is as many as one hundred and twenty features that have been described in Down syndrome though most individuals with the syndrome have no more than six or seven of these traits. These traits include flat round faces, eyes that slant upwards with an addition of a small fold of skin that runs vertically between the inner corner of the eye and the bridge of the nose, soft straight hair, small mouth cavities with large tongues, broad hands with short fingers and only one palm crease, hypotonia (floppy limbs), and low birth weights. .
Down syndrome is the most frequently occurring chromosomal abnormality in the world even though Down syndrome is not inherited by genetics but is a genetic defect that occurs randomly. Occurring more in boys the disease occurs once in every 700 to 1,000 live births affecting all ages, races and economic levels. There are about 4,000 to 5,000 babies born with Down syndrome in the United States alone annually affecting 350,000 families. Women over the age of thirty -five are more likely to have children with Down syndrome but eighty percent of children with Down syndrome are born to women under the age of thirty-five. The exact causes of the chromosomal rearrangement are unknown; it occurs when the chromosomes in an egg or sperm do not divide properly causing an extra chromosome twenty-one. However it has only been verified of paternal cause in only 5% of instances. It is assumed then the primary cause is maternal.
