I think you may be thinking of the relationship between down syndrome and maternal age, which I have heard estimated at "thousands of times more likely". Howev

I think you may be thinking of the relationship between down syndrome and maternal age, which I have heard estimated at "thousands of times more likely". However, perhaps this is a slight exaggeration as well: http://pregnancy.about.com/cs/downsyndrome/l/bldownssyn.htm http://pregnancy.about.com/cs/downsyndrome/l/bldownssyn.htm