I'm pretty sure that so long as the yolk is still intact (kinda hard to tell from outside the egg, right?), the baby won't suffocate or drown in fluid, but I do know (not yet from personal experience) that some breeders slit all of the eggs once one or more of them start to pip.

As far as slitting goes, I know that the idea is not to cut any of the veins, just the outer shell. I'm sure someone will chime in soon with exactly how to do it.