The traditional philosophy of the Roman Catholic Church holds that the rational soul is created at the moment when it is infused into the new person.
Thomas Aquinas, following Aristotle's embryology, taught that rational soul is created when the antecedent principles of life have rendered the foetus an appropriate organism for rational life, though some time is required after birth before the sensory organs are sufficiently developed to assist in the functions of intelligence.
[3]Philo and some rabbis insisted that God’s providence remains active, keeping all things in existence, giving life in birth and taking it away in death.
Hugh of Saint Victor and Alexander of Hales alone characterize Creationism as the more probable opinion; all the other Schoolmen hold it as certain.
[1] Gottfried Wilhelm Leibniz argued that Creationism guards the dignity and spirituality of the rational soul, and is the proper seat of the image of God.
[1][5] This view is generally held by the contemporary magisterium of the Roman Catholic Church, most notably in the instruction Dignitas Personae.