Infants don't avail anything. They're infants. God either provides for them or He doesn't. I'm convinced He does.
And I don't believe an aborted baby is availed to "Limbo".
Agree..A lot of concepts , such as limbo , are man made and not the word of Jesus. The 12/13th century cChurch can up with a lot of "funny" comcepts that have nothing to do with the message of the Christ.