it appears you are coming from an area/culture where this idea is ridiculous or unheard of.
i can assure you i meant what i said. there is absolutely nothing wrong with having children at 20, or even earlier. however it requires a community and a society that is supportive of that. it works very well in china, because the culture there does support it.
traditionally, the young couple lives together with the husbands family and can rely on their guidance and support raising the children. this way there is no problem with the young parents continuing their studies or working, because the household is managed by the grandparents. where i used to live every morning i would see lots of grandparents who themselves where in their 40s or 50s playing with babies while the young parents were off to work.
i understand that in western culture of independence where every couple lives on their own away from the grandparents, and with jokes about in-laws, this is hard to imagine. but really this is a different way to look at life and i believe it has many advantages.