An extra chromosome can cause a chromosomal condition, which is an alteration in the number or genetic structure of chromosomes. Trisomy is a type of chromosomal condition where the affected person has three copies of one of the chromosomes instead of two, resulting in 47 chromosomes instead of 46. Down syndrome, Edward syndrome, and Patau syndrome are the most common forms of trisomy. The extra chromosome can cause physical features and developmental challenges that can occur among people with Down syndrome. Children affected by trisomy usually have a range of birth anomalies, including delayed development and intellectual disabilities. The most important risk factor for trisomy conditions is maternal age, and women in their late 30s and 40s have a higher chance of trisomy conditions occurring. The effects of an extra chromosome can vary depending on the specific abnormality, but they can cause problems with growth, development, and function of the bodys systems.