What are Down syndrome tests?Down syndrome is a disorder that causes intellectual disabilities, distinctive physical features, and various health problems. These may include heart defects, hearing loss, and thyroid disease. Down syndrome is a type of chromosome disorder.Chromosomes are the parts of your cells that contain your genes. Genes are parts of DNA passed down from your mother and father. They carry information that determines your unique traits, such as height and eye color.People normally have 46 chromosomes, divided into 23 pairs, in each cell.One of each pair of chromosomes comes from your mother, and the other pair comes from your father.In Down syndrome, there is an extra copy of chromosome 21.The extra chromosome changes the way the body and brain develop.Down syndrome, also called trisomy 21, is the most common chromosome disorder in the United States.In two rare forms of Down syndrome, called mosaic trisomy 21 and translocation trisomy 21, the extra chromosome doesn't show up in every cell. People with these disorders usually have fewer of the characteristics and health problems associated with the common form of Down syndrome.Down syndrome screening tests show whether your unborn baby is more likely to have Down syndrome. Other types of tests confirm or rule out the diagnosis.
