Human persons who die unrepentant from actual mortal sin, or who die in a state of original sin alone, are sent by God to Hell, but they have different punishments.
Second Council of Lyons: “The souls of those who die in mortal sin or with original sin only, however, immediately descend to hell, yet to be punished with different punishments.”
Council of Florence: “But the souls of those who depart this life in actual mortal sin, or in original sin alone, go down straightaway to hell to be punished, but with unequal pains.”
Those who die in original sin alone have lesser punishments; this is usually termed the limbo (fringe) of Hell.
Pope Innocent III: “The punishment of original sin is the deprivation of the vision of God, but the punishment of actual sin is the torments of everlasting hell….” [Denzinger, n. 410.]
Notice that Hell is a place of “punishments”, even for those who die in original sin alone. Now the Catechism of the Catholic Church teaches that the chief punishment of Hell is the deprivation, which is given to all in Hell, even those in the limbo of Hell.
“The chief punishment of hell is eternal separation from God, in whom alone man can possess the life and happiness for which he was created and for which he longs.” [CCC 1035]
The CCC also teaches that human persons can only possess happiness with God, and that those who suffer the “chief punishment of hell” are eternally separated from God. This necessarily implies that no one in Hell can have happiness, not even in the limbo of Hell.
It is therefore contrary to Church teaching to claim that infants who die without baptism have perfect natural happiness in the limbo of Hell. The Church teaches that all souls in the limbo of Hell have the chief punishment of Hell, and specifically teaches that said chief punishment prevents them from having happiness.
However, the Church has never definitively taught that any children die in a state of original sin alone. This assumption that original sin alone applies to children is longstanding and found in many theological works, but it is not a teaching of the Magisterium.
And certain teachings of the Magisterium clearly imply that no children go to the limbo of Hell.
Pope Pius IX: “Because God knows, searches and clearly understands the minds, hearts, thoughts, and nature of all, his supreme kindness and clemency do not permit anyone at all who is not guilty of deliberate sin to suffer eternal punishments.” [Quanto Conficiamur Moerore 7]
Prenatals, infants, and young children are unable to commit deliberate sin, because they have no reached the age of reason. Therefore, according to the above teaching, they do NOT “suffer eternal punishments”. And since the limbo of Hell is a place of the chief punishment of Hell, they do not go to the limbo of Hell.
The universal salvific will of God is a dogma of the ordinary and universal Magisterium.
Cardinal Ratzinger: “In the New Testament, the universal salvific will of God is closely connected to the sole mediation of Christ: ‘[God] desires all men to be saved and to come to the knowledge of the truth. For there is one God; there is also one mediator between God and men, the man Jesus Christ, who gave himself as a ransom for all’ (1 Tim 2:4-6).” [Dominus Jesus 13]
All who are saved are saved by Christ, and God does in fact desire all human persons to be saved.
Pope John Paul II: “The universality of salvation means that it is granted not only to those who explicitly believe in Christ and have entered the Church. Since salvation is offered to all, it must be made concretely available to all.” [Redemptoris Missio 10]
And this implies that God gives every human person a concrete path of salvation. What is the path of salvation for prenatals who die in the womb? They cannot receive a baptism of water. They are too young by far to have baptism by desire. Either they receive a baptism of blood, or the universal salvific will of God fails in billions of cases. Therefore, they receive a baptism of blood.
The Church has never taught that prenatals, infants, and young children die in original sin alone. The Church has never restricted a baptism of blood to adult martyrs. The Holy Innocents received a baptism of blood, and though they died for Christ, they certainly did not know and choose to die for Him. So it is that the mercy of Christ grants to all prenatals, infants, and young children a baptism of blood, prior to death, so that they die in the state of grace and can have eternal happiness in Heaven.
Our merciful Savior, Jesus Christ, has no reason to deny a baptism of blood to billions of innocents, who, as Pius IX says, are “not guilty of deliberate sin” and therefore do not “suffer eternal punishments”. Billions die from abortion over the decades. Do you think abortionists have the power to deny heaven to unborn children? Billions die from natural causes (early pregnancy loss; miscarriage). Why would God deny them heaven?
Who then dies in a state of original sin alone? The CCC teaches that all who go to Hell are guilty and unrepentant of actual mortal sin (CCC 1037). Therefore, those persons only die in original sin who are guilty of the actual mortal sin of omission of never having found sanctifying grace in this life, despite ample opportunity. Lacking ample opportunity, the sin is not actual mortal. No prenatals, infants, or young children have had that ample opportunity, so none of them are sent to the limbo of Hell, a place of eternal punishments.
The only path to Heaven for prenatals who die in the womb is by a baptism of blood. And since God wills all to be saved, and that is the only way, then they must be given a baptism of blood. Therefore, the baptism of blood is not limited to adult martyrs. But if billions of prenatals are given a baptism of blood, when they die in the womb, there would be no reason to deny the same to infants who are newly born, but unbaptized. For it is the fault of adults, not infants or young children, when they are not baptized with water. Thus, all prenatals, infants, and young children who die without water baptism, receive a baptism of blood, and have eternal happiness in Heaven.
Is it possible they go to the limbo of Hell? No, that would contradict the teaching of the CCC and of Pius IX above. Is it possible they have perfect natural happiness in a version of limbo that is not Hell? No, that would contradict the teaching that we can only possess happiness with God in Heaven. Those who die in a state of original sin alone do not have the state of grace, do not have love, faith, and hope, do not have the company of God, the holy angels, and all the Blessed in Heaven, and they are not (as some have claimed) unaware of their condition, since the particular judgment tells each soul the truth about their life and their eternal destination. So the only possible answer is that prenatals, infants, and young children who die at that young age go to Heaven.
Whoever says otherwise contradicts the teaching of the Church.
What about St. Thomas Aquinas? He taught before the above teachings, before the Councils of Lyons II and Florence, before more recent teachings. So he was mistaken. We cannot follow the teachings of Saints or Fathers of the Church, when their opinions contradict subsequent magisterial teaching.