since you posted this question twice , im gonna put the same answer twice :) so for a mother ages 28 , there is a chance of 1 in 1000 , but at the age of 38 there is a chance of 1 in 200 . to work out how many times more likely it is for the 38 year old to give birth to a child with down syndrome is to divide 1000 by 200 and this gives us 5 . so the 38 year old is 5 times more likely to give birth to a child with down syndrome than a 28 year old :)