Have not read the thread beyond the OP. I'm not far off 60 now. I had my children when I was 30 and 32. We debated whether to have a third child and decided no. One of my reasons was that I'd heard that the chance of problems goes up markedly from the mid 30s. I would never have wanted to be pregnant in my 40s. Having said that, I was extremely fortunate to have met my husband when I was very young. Obviously for some people things work out differently.
What I wanted to say, though, was that if you have a baby in your 40s you will still have that child living at home with you when you are in your 50s and quite possibly 60s. That means dealing with a teenager while you are going through the menopause, which for many women is not a walk in the park.
Also, there really is a noticeable loss of energy as you get older. I know this is obvious, but it's easy to forget about it when you're younger. I look back to the sleepless years when my children were babies and toddlers and I marvel that we got through it. I really couldn't do it now. I am active and in reasonably good health but I have less strength and stamina than I had in my 30s.
Final point: if your parents are older, they are far less likely to want or be able to do hands on childcare for you, occasionally or as a regular arrangement. They simply won't be up to it in many cases. I'd give it a go if I had to, at my current age, but my parents are in their 80s and it's unthinkable that they could be asked to look after a tiny child for any length of time. That's been the case for many years now. They're fit and well for their age, they have all their marbles, but their mobility and their stamina levels just aren't up to being hands on grandparents, as they were when my children and my nieces and nephews were younger.