Ask most people about Jesus and his birth from a virgin mother and you are likely to get many answers.

It was prophesied… so it had to happen in order to fulfill prophecy and some might say it had to happen to show Jesus was supernatural.  Okay… but why was a virgin birth a MUST?

My friends at Interlink have summarized it here… because it really is a big, huge deal:

Warning! Theology ahead!
So, why is a virgin birth part of Jesus’ story?  Though some scholars include revealing God, bridging the chasm between God and humankind, saving humankind, and rescuing the whole creation as the purposes of the virgin birth of Christ, they are actually the purposes of the incarnation of Christ (why God became a man).
The virgin birth was the means of the incarnation of Christ (how God became a man). While the incarnation began at the birth of Jesus and continues forever, the virgin birth lasted only a matter of hours.
The distinctive purpose of the virgin birth of Christ was to free Him from the original sin in His incarnation (God becoming a man).
The ordinary processes of transmission of racial heritage were interrupted, in His case, by the miraculous conception.
But, we should not assume that the mere fact of a virgin birth would break the chain of sin. The unique circumstances associated with His birth help us to appreciate the fact that He was born without sin.
The Bible declares that He “knew no sin” (2 Corinthians 5:21); and “in Him there is no sin” (1 John 3:5).  Satan had nothing in Christ (John
14:30); he has no claim on the sinless Son of God.  Leon Morris rightly says: “Sin gives Satan his hold on men, but there is no sin in Jesus as in others.” (F.F. Bruce, Gen. Ed., The New International Commentary on The New Testament, 18 vols. Grand Rapids: Wm. B. Eerdmans
Publishing Company, 1984, Vol. IV: The Gospel According to John, By Leon Morris, p. 660)
Through the miraculous overshadowing of the Holy Spirit, Jesus was born sinless.  His conception served as a sign of the uniqueness of the Person who was born.  Jesus’ virgin birth and His deity are inseparably connected. If Christ were born in the natural way—that is, if He had a human father—He could not be God.  He would be just a human, and would have inherited the sinful nature. Jesus is God—not because He is born of a virgin; but because He is God, His incarnation had to be by way of a virgin birth.

So, yeah. A virgin birth. Really… it is a big deal… sinlessness of God as a man demanded a virgin birth (no human father).