Archbishop William Levada, the San Francisco prelate who earlier this year became the Vatican's guardian of doctrinal orthodoxy, told Pope Benedict XVI and a Vatican panel of theologians that a document on the issue might be published soon.
Limbo is the place where Catholics believe unbaptized babies go after they die.
The question was one that was important to Pope John Paul II, Benedict reminded the theologians who are part of the Holy See's International Theological Commission.
Catholics long believed that children who die without being baptized are with original sin and thus excluded from heaven. Theologians have taught that such children enjoy an eternal state of perfect natural happiness, a state commonly called limbo.
"In today's season of cultural relativism and religious pluralism, the number of non-baptized babies is increasing considerably," Levada said.
"In this situation, the paths to reach the way of salvation appear ever more complex and problematic," he said.
"The church is aware that salvation is uniquely achievable in Christ by means of the Spirit," said Levada. "But it cannot renounce reflecting on, in its role as mother and teacher, the destiny of all the men created in God's image, and in a particular way, on the weakest and those who are not yet in possession of the use of reason and of freedom," he said in reference to infants.
"The discussion in this sense has been very useful and one can well hope that in reasonably brief times, the study undertaken by the Theological Commission will yield a positive result, even in view of possible publication of a document about it," Levada said.
The Rev. Luis Ladaria, a Jesuit who is secretary-general of the commission, told Vatican Radio that "there isn't any binding Catholic doctrine" on the question of children who die without baptism.
"We know that for many centuries, it was thought that these children went to limbo, where they enjoyed a natural happiness but did not have the vision of God," Ladaria said in a radio interview.
"This belief, today, from recent developments not only theological, but also magisterial (teaching authority), is in crisis," Ladaria said. "We, thus, are now studying this problem knowing that it is a point upon which there has not been a definitive pronouncement."
Benedict is continuing his campaign to safeguard doctrinal orthodoxy in the Catholic Church, saying its theologians must follow church teaching and submit to its authority.
Benedict was the Vatican's top guardian of orthodoxy for two decades as head of the Congregation for the Doctrine of the Faith, before becoming pope in April. He named Levada as his replacement in that post.
Theology "always exercises itself in the church and for the church," Benedict told the commission. "The work of the theologian, must, therefore, be carried out in communion with the living voice of the church, that is, with the living magisterium of the church and under its authority."
Magisterium refers to church authority to teach truths. "To consider theology a private affair signifies disregarding its very nature," the pontiff said.
Under John Paul II, the Vatican cracked down on dissident theologians.
The commission this week has also been grappling with the concept of natural moral law.
That argument "is of special relevance in understanding the basis of rights rooted in the nature of the person and, as such, derived from the very will of the God creator," Benedict said.