The dogma of the immaculate conception means that Virgin Mary was conceived in the womb of her mother Anne and that she was removed from the original sin by sanctifying grace in the moment of her passive conception. The theologians of the Christian East consider the Virgin Mary as completely without sin, either personal or original.
But the leave the question unanswered concerning the moment when her sanctification happened. The agree it was in the womb of her mother Anne before the annunciation.