Becoming a mother in one's fifties is thought to be problematic for a number of reasons. The first is that it's not good for the resultant child. There are the trivial drawbacks such as having parents who are less energetic and more embarrassing. But there is also the serious issue of having parents who are likely to die before the child has a chance to provide them with grandchildren.
But, of course, youth is no guarantee of fitness and boundless energy. Lots of younger parents have neither the time, the energy nor the inclination to run around with their children. Lots of parents (actually, most of them) are a source of intense embarrassment to their children. And none of us can be assured that our parents will necessarily be around to see us into our thirties. Part of the problem here is that we seem to regard people who reach retirement age as being at death's door. But most will be only three quarters of the way through their lives.
One or two commentators voiced concern for the physical health of the mother and suggested that embarking upon pregnancy was rather foolhardy. It is no doubt the case that the older the mother, the more risky the pregnancy and birth. But when younger mothers put their own health at risk for the sake of their child's, we usually regard them as courageous, not foolish.
The final objection to postmenopausal mothers is more nebulous, but it boils down to the idea that it is just plain wrong, either because such women are 'straying over nature's line' or because they are selfish and obsessive.
But since when was having children a purely selfless act? Most of us are motivated by a combination of factors: some wonderfully high-minded, some selfish, or others largely inexplicable. Few of us are ready for parenthood, even when we plan it exhaustively, and most of us worry whether we're doing it right.
The one thing most parents enjoy, however, is the freedom to have and to bring one's children up in their own way, according to their own values and preferences. Unless society can ascertain that postmenopausal mothers are clearly going to have a damaging effect upon their children (which it cannot), there seems little justification for not just letting them get on with it.