Your infallible Church allowed St. Bernard to remain in ignorance of this doctrine.

Since the Church had not then given any infallible definition on the subject St. Bernard naturally could not be guided by it. St. Bernard believed that Mary was born free from sin, but he was puzzled as to the moment of her sanctification. He thought the probable explanation to be that she was conceived in sin, but purified as was St. John the Baptist prior to her actual birth. But he did not regard this opinion as part of his Faith. Meantime his error was immaterial prior to the final authentic decision of the infallible Church. St. Bernard believed all that God had taught and all that the Catholic Church had clearly set forth in her definitions prior to his time.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty