In which population is Down syndrome most commonly diagnosed?

Down syndrome, or trisomy 21, is most commonly associated with maternal age. The incidence of Down syndrome increases significantly with advancing maternal age, particularly for women over the age of 35. The underlying reason for this increased risk relates to the likelihood of nondisjunction during meiosis, which can occur more frequently in older oocytes. As a result, children born to older mothers are more likely to have chromosomal abnormalities, including Down syndrome, compared to those born to younger mothers.

Other options do not accurately capture the primary factor associated with Down syndrome diagnosis. Environmental factors and lifestyle choices have not been demonstrated to have a direct link to the incidence of Down syndrome, as it primarily arises from genetic factors rather than lifestyle or environmental influences. Genetic testing is instrumental in confirming a diagnosis of Down syndrome, particularly if a chromosomal abnormality is suspected, but it does not represent the population most commonly diagnosed with the condition.