¿What is Down syndrome?
Down syndrome is a chromosomal disorder that includes a combination of birth defects, including some degree of intellectual disability, characteristic facial features and, often, heart defects and other health problems. The severity of these problems varies greatly among affected individuals.

¿How often occurs in Down syndrome?
Down syndrome is a genetic birth defects more common, affecting about one in 800 babies (approximately 3,400 babies) annually in the United States.1 According to the National Society of Down Syndrome (National Down Syndrome Society ) in the U.S. There are over 400,000 individuals Down.2 syndrome

¿What causes Down syndrome?
Down syndrome is caused by the presence of extra genetic material on chromosome 21. Chromosomes are cellular structures that contain genes.
Normally each person has 23 pairs of chromosomes, or 46 in total, and inherits a chromosome pair of the ovum of the mother and one father's sperm. In normal situations, the union of egg and sperm results in a fertilized egg with 46 chromosomes. Sometimes things go wrong before fertilization. An egg or sperm development can be divided incorrectly and produce an egg or sperm with a chromosome number 21.
When the sperm unites with a normal egg or sperm, the resulting embryo has 47 chromosomes instead of 46. Down syndrome is called trisomy 21 because affected individuals have three # 21 chromosomes instead of two. This type of accident in cell division produces about 95 percent of Down syndrome cases.