Late 30s, early 40s is really late for children. Something I will teach children is that real life has time limits and it's important to be aware of them.

It's all doable, of course, but all risk has increased. One thing I would do in my life on a do over is start earlier.

Late 30s you're playing on hard mode. Early 40s, you've got to sperm donor that and solo it (which a friend of a friend is doing). The time risk is very high!