18 This is how the birth of Jesus Christ came about: His mother Mary was pledged to be married to Joseph, but before they came together, she was found to be with child through the Holy Spirit. 19 Because Joseph her husband was a righteous man and did not want to expose her to public disgrace, he had in mind to divorce her quietly.
20 But after he had considered this, an angel of the Lord appeared to him in a dream and said, “Joseph son of David, do not be afraid to take Mary home as your wife, because what is conceived in her is from the Holy Spirit. 21 She will give birth to a son, and you are to give him the name Jesus, because he will save his people from their sins.”
22 All this took place to fulfill what the Lord had said through the prophet: 23 “The virgin will be with child and will give birth to a son, and they will call him Immanuel” —which means, “God with us.”
I've never had a major problem with the idea of the virgin birth. If you buy into the notion of a Creator, then you have a God who is in the miracle business from the get-go. Even a guided evolution version of Genesis has God tweaking the mutations via some miraculous genetic engineering in order to get the job done.
Fast forward a few millennia to Jesus' incarnation; suddenly, God has to lay back and let his Son get seeded through some illicit nik-nik? No, that's writing one too many miracle out, at least.
God was (and is) in da house, sending a part of Himself to die for us. That's the core of the Gospel.