in the womb can affect kids regardless of other factors. I'm glad your kids lucked out in that area. But some mental illnesses you are born with and they show up at a very early in age. I know from experience and have seen it in many others.
Again, I agree that good health practices can be a great benefit since the brain is still developing when young, but genetics/luck of the draw of how your brain develops in the womb play a big role.