If they find a difference in your baby s DNA (a missing bit or extra bit), they may check your DNA and your partner's to see if either of you also have it. If you or your DH have the same change, it might mean that it is just a variation that doesn't cause disease. If neither of you have it, it might mean that the change happened only when your baby was made (in the egg or sperm or when they got together), and this might be why she got sick.

Genetics knowledge has come so far, but there is still so much that isn't known as well.