Oh, it's the cutoff at the other end...
Well, personally I don't intend to have any more kids - but that's nothing to do with age, and everything to do with freedom!
I can't really see why you need a cut-off. If we spent all our time looking at risk factors and what-ifs then we'd never do anything. Anyone can get sick, anyone can have an accident, babies can have issues whatever the age of the mother (or father). I know plenty of women in their late 40s with babies, I know plenty of grandparents who take major roles in child-rearing, it seems to me that a cut-off is just putting more pressure on people for no decent reason.