Henry Imler posts some arguments from N.T. Wright in favor of the historicity of the virgin birth accounts. I don't think I've seen these arguments before. He lists three. The first is more an argument against arguments against the virginal conception. The other two actually support the historicity of the virgin birth passages in Matthew and Luke, and those are what caught my interest:
2. Isaiah 7 was never part of any pre-Christian Jewish view of the Messiah being born of someone who was still a virgin by the time of the conception. Everyone who read the passage took it in the way that an ordinary person would. It says that a virgin would engage in sexual relations, conceive, and then give birth. In its immediate context about the children whose names are mentioned in that very passage, it had to mean exactly that. So no one thought of this as a messianic passage about someone who would conceive and then give birth, all while remaining a virgin. But what that means is that it's extremely unlikely that someone would concoct this legend about Jesus being born of a virgin to fit a prophecy that no one interpreted that way. When people invent circumstances to fit a prophecy, they don't usually recast an already existing prophecy in a way that no one interpreted it. It would be one thing to look back on Isaiah 7 if a virginal conception happened. It would be quite another thing to interpret it anew without any such an event. Why insist on taking a passage in a way no one had before if it's not to explain an event that makes much more sense with the newfangled interpretation?
2. Matthew and Luke record two very different sets of traditions about the birth of Jesus. If they were importing a pagan myth because of some theological value, it would be surprising to find no theological hay made of it in either of the two very different literary traditions. But yet that's what we have. Even if the authors of the two accounts didn't think it was a pagan importation but believed it, it would be strange that this was done earlier for theological purposes and yet neither account would actually include such reasons or any sign that there ever were any. What would be more likely is that they didn't believe it because of its theological significance but believed it simply because it had its basis in actual events.