Ah, a place I can jump in!
One’s unrepentant sin sends someone to Hell. We send ourselves to a warm (or cold if you like Dante) isolated place for eternity. (Note, this does not mean the opposite happening is automatically also our choice, it is not, that one is God’s).
It is also Church teaching to use Faith and Reason.
Thus, as a father of a miscarried little guy, I know he didn’t get an opportunity to sin or repent on earth.
I can only have hope that when presented with whatever information a dead person is presented with, he chose God’s side.
Why would I think my son has a choice after death?
If God Created him, he probably wants him and loves him.
If God loves him, that love can’t include a forced return of love by my son.
A forced action upon my son can’t be love, that would be slavery.
Now it would seem the cards are a bit in God’s favor in this case because whatever is presented to him, my son doesn’t have a lifetime to weigh against and thus hopefully didn’t take long to make a decision to hopefully love God back prior to judgement (which would seem to be a formality without a life lived).
With this reasoning, I think it is fair to say my son is in Heaven.
You might want to research the ccc about your ‘well known fact’.
usccb.org/beliefs-and-teachings/what-we-believe/catechism/catechism-of-the-catholic-church/index.cfm
I don’t think you’ll find anything that guarantees hell but for a sinner who chooses it in a lifetime of unrepentant rejection of God and His laws.
Take care,
Mike