First of all, this was never official Catholic teaching.

Some theologians did posit the idea of limbo, a sort of neutral existence between heaven and hell, for those who died before being baptised, because they wanted to make Baptism the sacrament which opened the doors of heaven to us. Today the Church emphasises the love of God. We are perhaps less certain than previous generations that we know what happens to us after death. But we are content to leave this mystery in the hands of God who loves each person and who would not abandon one of his little ones.

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