If they had the choice to not suffer, and they wanted to take it, then I think it's their decision to make, and not anyone else's

But the moral conundrum here is that they can't choose untill well after they're born, meaning the parents are the ones that need to make the decision.

This is one of those situations where the child will likely never get the choice, for the same reasons we don’t require informed consent for being born or getting your diaper changed.

By the time they can make it, it’s too late.

I would to add onto what others have said by mentioning that omission is still a decision. Even if the parents didn't explicitly choose, the inaction comes with dire consequences towards the child, whose parents are responsible (and held accountable) for taking care of.