I'm honestly not sure how familiar you are with midrash and prooftext. So,
Joel M. Hoffman writes:
As it happens, Isaiah 7:14 is compatible with a virgin birth, because a young woman could be (and often was) a virgin. But, more interestingly, I don’t think it matters.
The reason it doesn’t matter is that a “proof text” — that is, a scriptural citation that reinforces some particular point — isn’t meant to prove something in the modern, scientific way that we usually now consider proof. Rather, the proof text just has to match.
Certainly, the parthenos (“virgin”) of the LXX translation of Isaiah matches the virgin birth in Matthew. And, almost as certainly, Matthew knew that his proof text only worked in Greek. He didn’t care. A proof text isn’t scientific. It’s religious.