http://www.slate.com/blogs/blogs/humannature/archive/2008/05/19/incest-and-delayed-motherhood.aspx
..."By age 45, the probability of Down syndrome alone roughly matches the 4 percent cumulative risk of birth defects from cousin marriage"....
..."By age 45, the probability of Down syndrome alone roughly matches the 4 percent cumulative risk of birth defects from cousin marriage"....