The genetic risk from first-cousin unions depends on repetition of the practice down generations. There is a similar level of genetic risk resulting from the practice of western women having their babies older and older. If you have a baby at 40 you're taking approximately the same risk as you would be in a one-off first-cousin union. You're taking risks for your baby if you drink, smoke or abuse substances, or if you're obese or otherwise malnourished. I'm interested to know why this particular issue has been homed in on here. No, let me guess....