I had my first at 42, second at 45, and about to have my third at 48. Honestly it’s been fine - thinking that people might find this unimaginable is so far from my reality. It really feels like I’ve had the same experience as those in their 30s.
Part of this might be that 40s life is a bit more chill anyhow - I no longer go and get smashed every weekend, or even have the FOMO that I’m not doing that. And work life, whilst more junior, was ultimately more extreme in my 20s and 30s. So any physical drop is probably balanced by a slight drop in general burning the candle at both ends.
But yeah, don’t think 40s parenting is a no go. Go for it!