Final answer:
The risk of having a child with Down syndrome increases after a woman reaches the age of 35, due to age-related nondisjunction events during cell division leading to trisomy 21.
Step-by-step explanation:
The chances of a woman having a child with Down syndrome begin to increase rapidly after the age of 35. Down syndrome, also known as trisomy 21, occurs when there are three copies of chromosome 21 instead of the usual two.
This chromosomal abnormality is more likely to happen due to nondisjunction events during cell division, which become more frequent as a woman ages.
It's important to recognize that despite the challenges, individuals with Down syndrome can lead fulfilling lives and be active members of society. The risk factor associated with mother's age is critical for prospective parents to consider, although lifestyle factors may also play a role.