The total number of cases at birth in the US increased by 24.2% from 1979-1983 to 1999-2003. Atrioventricular septal defect affects 40% of DS patients. The trisomy of chromosome 21 is the cause of 95% of Down syndrome cases. The average life span of a person with DS is 49. The age of is 45 or older the risk is 3.6 percent more likely. Congenital Heart Disease affects about 40% of DS patients. In 88% percent of cases the extra chromosome 21 is from the mother.
