Extracted text: Table 1: DOWN SYNDROME BY SINGLE-YEAR INTERVAL Down syndrome live births, and estimated total live births, for British Columbia residents, 1961-1970 Matemal age in years Sum total of live births Sum total of cases S17 18 19 13,555 13,675 18,752 16 15 16 20 21 22,005 23,896 24,667 24,807 23,986 22 16 12 17 22 22 23 24 25 26 27 28 29 22,860 21,450 19,202 17,450 15,685 15 14 27 14 9 30 31 32 33 34 13,954 11,987 10,983 9,825 8,483 12 12 18 13 11 35 36 37 38 39 7,448 6,628 5,780 4,834 3,961 23 13 17 15 30 2,952 2,276 1,589 1,018 596 40 31 41 33 20 16 22 42 43 44 45 246 327 249 11 7 Total 354,880 519 *5 mothers of age 46 years, 2 mothers of age 47 years with Down syndrome live births.
Extracted text: In this section population data on the incidence of Down syndrome in relation to mother's age will be analysed in detail. These observations should allow you to more fully understand the statistical probability of this common autosomal aneuploidy (which you will learn more about in week 11). The population data in Table 1 shows the total number of children born and the number of Down syndrome children born to mothers who have been classified into single year intervals of their age at the time of birth. The data are from residents of British Columbia, Canada and were collected for the years 1961 to 1970. (Note: This was before prenatal diagnosis was available.) Q8. Calculate the overall rate of occurrence of Down syndrome per 1,000 births. Give your answer to two decimal places. Q9. It is sometimes forgotten that many Down syndrome children are born to younger mothers. What percentage of Down syndrome children in the British Columbia study were born to mothers younger than 37 years? Give a whole-number, no decimal places. Q10. If 2,000 children are born each year in Victoria to mothers who will be 37 years or older, and if the mother's age distribution follows that of the British Columbia study, how many Down syndrome children would be born to such mothers in one year (in the absence of prenatal diagnosis and intervention)? Give a whole-number, no decimal places.