Down syndrome or Down's syndrome, also called trisomy 21, is a genetic sickness resulting from the presence of all or part of a third replica of chromosome 21. it also includes related to physical growth delays, slight to slight highbrow disability, and function facial capabilities. The common IQ of a younger grownup with Down syndrome is 50, equivalent to the mental ability of an eight- or 9-year-old toddler, however this may range extensively. The mother and father of the affected man or woman are usually genetically normal. The possibility will increase from less than 0.1% in 20-year-vintage moms to 3% in the ones of age 45. The more chromosomes is believed to arise by way of chance, with no known behavioural pastime or environmental factor that adjustments the possibility. Down syndrome can be identified for the duration of pregnancy by way of prenatal screening observed through diagnostic checking out or after birth by direct statement and genetic testing. For the reason that creation of screening, pregnancies with the prognosis are frequently terminated. Ordinary screening for fitness issues common in Down syndrome is recommended throughout the person's life.