You should keep in mind that Down syndrome is "not really" a congenital disease. Yes, it's a DNA problem, but it's a problem that happens during conception in the logic of recombining DNA, not in the DNA itself. Down is "Trisomie 21". Which makes it very weird: it a congenital disease, but not hereditary (perfectly healthy parents can have a Down syndrome kid, especially if the mother is older, Down syndrome parents have normal offspring)
So there are congenital diseases ... and there is Down syndrome. They follow an entirely different logic.
Btw: down syndrome parents have HUGE issues, but in fact these issues arise because the kids are healthy. Expectation is such kids will exceed their parents' intelligence at age 6-8 and be 2 standard deviations above their parents intelligence by age 10-12. You can imagine how that goes.
So there are congenital diseases ... and there is Down syndrome. They follow an entirely different logic.
Btw: down syndrome parents have HUGE issues, but in fact these issues arise because the kids are healthy. Expectation is such kids will exceed their parents' intelligence at age 6-8 and be 2 standard deviations above their parents intelligence by age 10-12. You can imagine how that goes.