Why are people annoyed by this question? No one has to answer it or read the thread.
People are said to regret the things they didn't do more than the things they did do that went wrong. I don't know how much research that's based on. But it makes sense to me, looking back over my life. The memory of disasters tends to fade over time, sometimes ending up as an amusing anecdote. But opportunities not taken, things you wanted to do but didn't quite have the nerve -- those still have a sharp sting when I bring them to mind.
My friend A, happily married for some years, got pregnant without difficulty in her late 30s. She told me she couldn't make up her mind till then; her husband was easy either way. And in the end, she decided she would regret her decision more if she didn't than if she did. All turned out well and she has never regretted it. On the other hand, she says very honestly, she might well have regretted it if the baby had had serious health or other problems.
My friend B had infertility treatment before her longed-for children were born. They are now grown up, and she loves them, but says she would probably have been just as happy if she hadn't had children. But you can't know that in advance.
I wasn't bothered about having children when I was young, then gradually changed my mind in my 30s, but left it too late to actually do it. And I do regret that.
One other point: as you grow older, the few years you spent looking after a child becomes a smaller and smaller chunk of your life. And even in those child-rearing years, you do other things too -- it doesn't take up 100% of your time for long.
My friend A's outlook may sound cold, but I don't think it is really -- it makes a lot of sense. I tend to agree that it's the things you don't do that you regret most.