The Scriptures explicitly says “he will be filled with the Holy Spirit, even from his mother’s womb.” (Luke 1:15). The indwelling of the Holy Spirit who sanctifies us is incompatible with original or mortal sin. Tradition holds this happened when Mary, pregnant with Jesus, visited Elizabeth and John leapt in the womb.
For example, Pope Leo XIII confirmed this in the encyclical Iucund Semper Expectatione:
Then St. John the Baptist, by a singular privilege, is sanctified in his mother’s womb and favored with special graces that he might prepare the way of the Lord; and this comes to pass by the greeting of Mary who had been inspired to visit her cousin.