The problem is that when parents have children in their teens and 20s, the children are much more likely to be healthy, and if the parents have children in their late 30s or 40s, the children are more likely to be sick.

So couples who decide "well, we're broke, but we'll figure it out" tend to have healthier children because they have them at younger ages.

At the risk of being controversial and making people angry, this happened quite a bit in the USA and it caused tension: many white people went to college, dated around, joined the work force in their mid 20s, married in late 20s and then got a home, and then had children in their early 30s. On the other hand, immigrants who didn't go to college and did jobs that immediately resulted in decent wages but were not white collar or prestigious, often had children in their early 20s. I believe it was part of the reason for the racist backlash that happened with Trump's election: it wasn't just too many immigrants, it was too many and they were doing too well and somehow thriving.

The again, this is my personal view without data. This could be tested by looking at things like autism and disability rates of children of young parents versus older parents.

This isn't about race; instead I am saying this idea that having children at a young age is bad because it's financially irresponsible goes against instinct and is often a bad choice for the children. Better to be a poor healthy child than a sick rich child.

Also, the average human has something like 7-11 genetic defects, so it's normal to have a certain amount of genetic errors. But children of older parents are likely to have more.