Roman Catholic AnswerThere are three defined dogmas concerning the Blessed Virgin Mary:
1) At the Ecumenical Council of Ephesus in 431 A.D., in response to the Nestorian heresy, the Council defined Mary as Theotokos, "the Mother of God".
2) In 1854, in his bull Ineffabilis Deus, Pope Pius IX infallibly defined the doctrine of the Immaculate Conception.
3) In 1950, Pope Pius XII, in his Apostolic Constitution, Munificentissimus Deus, proclaimed the dogma of the Assumption of Mary.