I wonder whether there is a difference in the probability of defects when the mother is older when you compare completely natural conceptions to those that are medically assisted (hormones, artificial insemination, IVF, etc). Seems to me that if a woman just "gets pregnant" when she's in her 40's, that's a pretty good sign that things are still working the way they do for younger women- Is it possible that a woman who just conceives in her 40s has a better chance at a healthy baby then a woman who requires a lot of intervention in her mid-30s? (I have no idea, just curious)