Designer Babies

While I wouldn't mind supporting giving babies more resistances to diseases, the problem is, what if you code it wrong, or something goes haywire in the DNA that you didn't/couldn't predict?

Suppose you activate some genes so that you're very resistant to most infections. But what if by doing that, you make an overzealous immune system that attacks anything that wasn't produced by your body (so much for transplants and blood transfusions)? And what if they're so overzealous that they attack your own cells? I wouldn't want to have my immune system suppressed my entire life, and then be forced to live in a bubble to survive.

Or what if you accidentally make it so that the genes age at twice the normal rate? I don't think too many people would like that, only being able to live half as long as most other people if they otherwise lived healthy lives.

Sure, I can see the upsides to that, but like others said, there are those who will inevitably create or want "designer babies", and by playing God, who knows what could potentially happen? We could either end up with real X-men, or have people that have really strange and weird diseases.

Jam it back in, in the dark.