There are plenty of older parents.
She must have had her first baby at a young age - 25? Loads will come on to say thats an average age, but in my circle, that is considered a young age.
I know a relative who had two children and then waited 15+ years before having another two. Like someone already posted, it was because they didn't want the third child to grow up effectively as an only child.
I'm in my late 40s and no sign of the menopause yet. For all those saying, they'd couldn't be paid enough to have more children, I would think the Ramsays experience of raising kids is very very different to the rest of us Night nurses, cleaning staff, admin staff, multiple homes, nannies, private schools, - it must be wonderful to have children with all that support.
For me, the biggest issue would be the risks involved. It must be very hard to do the necessary tests to see if the child will be healthy because if she wants babies so much (and she obviously does), weighing up the factors while deciding whether to proceed or not must have been very very tough.