Final answer:
The next most common trisomies after Trisomy 21 are Trisomy 18 (Edwards syndrome) and Trisomy 13 (Patau syndrome), both associated with severe disabilities and short life expectancy. The risk of trisomies increases with maternal age.
Step-by-step explanation:
Other than Trisomy 21, which is known as Down syndrome, the next most common trisomies that can be observed at birth are Trisomy 18 (Edwards syndrome) and Trisomy 13 (Patau syndrome). Both of these conditions result from an extra copy of their respective chromosomes. Individuals with Trisomy 18 or Trisomy 13 tend to have severe intellectual and physical disabilities and often have a very short life expectancy. Trisomy 18 is associated with developmental delays, growth deficiency, and a variety of malformations, whereas Trisomy 13 involves severe intellectual disability and physical abnormalities such as cleft lip and palate, polydactyly, and heart defects. The likelihood of nondisjunction, which causes trisomy, increases with maternal age, especially in females over 35 years old.