[Feldkurat_Katz]

For most people, it does not make sense to have children in your 20s

For women, early 20s are biologically the best time for having children. Men are a different story, though.

[Melas]

Actually, physiologically speaking, your sperm is the most robust and healthiest between 16 and 20, so it's no different for men.

[tortoise]

For women, early 20s are biologically the best time for having children.

Unfortunately, it is unambiguously almost the worst time by most other important metrics. Our environment is evolving faster than our biology.