The incidence of a child being born with Down syndrome to a mother at age 35 is 1 in 500 births. The risk at maternal age 45 is 1 in births.

Question

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The question lists the incidence of Down syndrome at maternal age 35 (1 in 500) and asks for the risk at age 45. As maternal age increases, so does the risk of having a child with Down syndrome. It is known that the risk doubles from age 35 to age 40, and then doubles again from age 40 to age 45. Therefore, the risk at age 45 is approximately 1 in 18 births. The correct answer is D.

The Incidence of a Child Being Born with Down Syndrome