In reply to Justin Walker.

Dear Justin,
While the thrust of the argument is not, specifically, a defense of the perpetual virginity of Mary [semper virgo; FC SD VIII, 24], there is ample room in both our Confessions and LCMS history and practice for such a belief. The FAQ cited above seems unaware of Francis Pieper's statement in his dogmatics text--the same text that nearly all LCMS pastors use in their seminary training--which states, "If the Christology of a theologian is orthodox in all other respects, he is not to be regarded as a heretic for holding that Mary bore other children in a natural manner after she had given birth to the Son of God." (Christian Dogmatics II:308)
Beyond this, I'd encourage you to read up a bit on the history of the question. I think you'll find it both interesting and fulfilling. Jerome's writing against Helvidius might be a good place to start for the early tradition. A more recent work of a scholarly nature is John McHugh's "The Mother of Jesus in the New Testament."
Peace!