Isaiah 7:14, so 700+ years before Christ or the Apostles walked the earth.
Not hard!
That was the prophecy and not the actual fulfillment that was witnessed by the Church. It’s important that you pointed that out though ,dear friend.
We can also use the typology to give credibility too.
Like this ...
There was a virgin, Gen 2:22-25 = There is a virgin, Luke 1:27-34
Shows the parralles to Mary as the New Eve coupled with the writings of the early church Fathers.
Such as....
“He became man by the Virgin, in order that the disobedience which proceeded from the serpent might receive its destruction in the same manner in which it derived its origin. For Eve, who was a virgin and undefiled, having conceived the word of the serpent, brought forth disobedience and death. But the Virgin Mary received faith and joy, when the angel Gabriel announced the good tidings to her that the Spirit of the Lord would come upon her, and the power of the Highest would overshadow her: wherefore also the Holy Thing begotten of her is the Son of God; and she replied, ‘Be it unto me according to thy word.’ And by her has He been born, to whom we have proved so many Scriptures refer, and by whom God destroys both the serpent and those angels and men who are like him; but works deliverance from death to those who repent of their wickedness and believe upon Him.” Justin Martyr, Dialogue with Trypho, 100 (A.D. 155)