Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
The Immaculate Conception is not synonymous with the virgin birth of Jesus, nor is it a supposed belief in the virgin birth of Mary, his mother. Rather, the Immaculate Conception is the Roman Catholic belief that Mary was not subject to original sin from the first moment of her existence, when she was conceived. The concept of the virgin birth, on the other hand, is the belief that Mary miraculously conceived Jesus while remaining a virgin.