Baby is born with an extra chromosome in each of its cells What is responsible fir this condition

These changes can occur during the formation of reproductive cells (eggs and sperm), in early fetal development, or in any cell after birth. A gain or loss of chromosomes from the normal 46 is called aneuploidy. A common form of aneuploidy is trisomy, or the presence of an extra chromosome in cells.

Explanation:

pregnancy happens more and more

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.