I've seen this episode before

Oo is this the one where barclay becomes a spider?!

could be, or the one where dr pulaski becomes an old lady...

Or the one where Tom Paris and Janeway turn into lizards and have babies.

i forgot about that one, that also reminds me, what janeway did to poor tuvix...

Honestly, the most likely thing is lots and lots of dead fetuses due to developmental abnormalities. I'd be surprised if it ever got to the point of resulting in a dead infant.

Quality control and testing is absolutely essential, yeah. It's hard work and the plan shouldn't be misconstrued as "rewrite the whole genome of an embryo today and go for the first birth immediately" because that would be stupid when we know there is other work to be done. It shouldn't surprise ANYONE that making significant progress against cancer, aging, or other issues, would take lots of work and not doing the immediate obvious broken thing.