Hi, Steven —

Thank you for your question.

The Church does not believe that Mary came about as a result of her Mother, St. Anne, having a Virgin Birth. However, the Immaculate Conception is a separate doctrine which involves Mary's conception in her mother, St. Anne's womb.

Mary's parents, Sts. Joachim and Anne, conceived Mary in the normal way, but the Church teaches that Mary was granted a singular grace of being conceived without the stain of original sin.
She was ** preserved ** from sin on the basis of what Christ was going to do on the Cross.
The Church calls this teaching, the Immaculate Conception.

To use an analogy, it was like salvation by credit. Where the rest of us were born with original sin, struggle with sin then we come to salvation through Christ, Mary was saved in a more glorious way. She was preserved, or prevent from falling into sin when she was conceived; this was an act of God's grace and was not due to anything of her own nature. The Church teaches that God did this so that Christ would have a fitting vessel for to enter the world.

Hope this Helps,

John C. DiMascio