Those words to Joseph were for his understanding. Mary already knew and said yes to God regardless of the consequences to herself.
Anyhow, that does not invalidate what I said nor change what happened and why it happened. Mary was in need of a Savior and Jesus was that Savior. The church has never taught any thing other than that Truth.
That is a lovely and sweet thought
shalom b'SHEM Yah'shua HaMashiach
but is does not seem to be supported by scripture.
It does not seem to be supported by your own Roman Catholic catechism. The doctrine of the Immaculate Conception. "The Gospel According to Rome". James G. McCarthy. Of Mary. "...in the first instant of her conception.. was preserved free from all stain of original sin..." Now that would be your Catechism paragraph [491]. - Pope Pius IX, Ineffabilis Deus.
And then there is the Annunciation, the angel Gabriel's announcement of Christ's incarnation to Mary: "Hail,full of grace, the Lord is with thee: blessed art thou among women" (Luke 1:28 Douay Rheims), Catechism 490-491. This says the Church, reveals that Mary "was never subject to the curse"* and that she was "immune from all sin, personal or inherited."**
* -Pope Pius IX, Ineffabilis Deus. **-Pope Pius X11, Mediator Dei. no. 73.
So just exactly was she in need of a Savior, if she had no sin to be saved from? And if this is true, why teach she had no sin, personal or inherited?