In children of unrelated couples, the risk of
congenital and genetic including recessive problems is usually estimated at about 2-3 per cent. First cousins have a higher risk of recessive problems in children than unrelated couples because they share 12.5 per cent of their genetic material and may have inherited the same mutation from a common ancestor.
Risk to their children is usually estimated at about double the risk of congenital and genetic problems in children of unrelated couples. At about 4-6 per cent, this doubled risk is also a 94-96 per cent chance that their child will be perfectly healthy. A cousin couple is thus more likely to have a healthy child than to have a child with a recessive problem.