As for babies and salvation. A person has to be old enough to understand right from wrong. A baby has no concept of that. They know hunger and discomfort from various causes. It's up to caring, loving adult to take care of their basic needs. Usually by early grade school age a child is able to understand right from wrong. Until then, they are under God's grace.
I can remember being held by my aunt as a baby who had said I was her other Mommy. My other aunt saw my look of confusion & had commented on it to my aunt that had said that.
I remember my Dad changing my diaper and complimenting me oddly about it that I did a good job. And I happily obliged him and did more of my duty and he was upset and angry about it and that made me cry.
I have heard of people saying they remember being in their mother's womb. I don't.
I can understand offenses and hurt and disappointment and confusion for which babies have to have understanding for confusion to come about.
Anyway, regardless, I believe His words that no man can come to the Son unless the Father draws him, including babies and I dare say even the unborn for God the Father can reveal His Son to the unborn if He wanted to since in sin, we have been conceived in our mother's womb. Psalm 51:6 seems to suggest, infer , and even imply that the Father can make us know the truth before we were even born bit Matthew 11:25 does testify. He can reveal His Son to babes to believe in Him & be saved.
Psalm 51:5 Behold, I was shapen in iniquity; and in sin did my mother conceive me. 6 Behold, thou desirest truth in the inward parts: and in the hidden part thou shalt make me to know wisdom.
John 6:44 No man can come to me, except the Father which hath sent me draw him: and I will raise him up at the last day.
Matthew 11:25 At that time Jesus answered and said, I thank thee,
O Father, Lord of heaven and earth, because thou hast hid these things from the wise and prudent, and hast revealed them unto babes. 26 Even so, Father: for so it seemed good in thy sight. 27 All things are delivered unto me of my Father: and no man knoweth the Son, but the Father; neither knoweth any man the Father, save the Son, and he to whomsoever the Son will reveal him.
I believe God the Father knows every one created to be born if they would want to be saved by God through Jesus Christ or that they prefer their evil deeds rather than to believe in Him to be saved.
There will be no one in Hell saying they would have believed if they had only known the gospel. They may want to send someone to warn their families like the rich man did in asking Abraham in Abraham's bosom but Abraham said that they have His words as he had and if they did not listen to His words, they would not listen to one even if risen from the dead because.. as I add to point out even for the rich man in hell, they'd prefer their evil deeds still.
Anyway, I believe God is God and no babies, unborn or otherwise will be in hell if they would have believed if they had only known the gospel when He would have drawn them unto the Son to believe in Him to be saved.
Saul met Jesus the way to Damascus and Muslims met Jesus in visions and revelations for why they now believe in Him to be saved, and so not so hard for the Father to reveal His on to babies, born or unborn to believe in Him to be saved.
At the rapture event, I dare say it may even be possible that an unborn child could be raptured without the mother, but I will know for sure when we are face to face with the Lord in Heaven.