Whatever Happened to Limbo?
What happened to the Church teaching about Limbo?
Limbo was never an official teaching of the Church, as The Catholic Encyclopedia, published in the early 1900s, makes clear. But it was a common theological opinion for a good number of years. Limbo describes a place where unbaptized children and those unbaptized persons who had reached the age of reason but had not committed mortal sin would go upon their deaths. It is not heaven yet it is a state of complete natural happiness.
For more on this subject, please see this article by Catholic Answers founder Karl Keating.