Matthew 1:18-20 "Now the birth of Jesus Christ was on this wise: When as his mother Mary was espoused to Joseph, before they came together, she was found with child of the Holy Ghost. Then Joseph her husband, being a just man, and not willing to make her a publick example, was minded to put her away privily. But while he thought on these things, behold, the angel of the Lord appeared unto him in a dream, saying, Joseph, thou son of David, fear not to take unto thee Mary thy wife: for that which is conceived in her is of the Holy Ghost."
In Isaiah 7:14, God promised us a sign concerning our Saviour. The Scripture tells us that “Therefore the Lord himself shall give you a sign; Behold, a virgin shall conceive, and bear a son, and shall call his name Immanuel.” The birth of Jesus Christ came in this manner (was on this wise) as a sign from God to His people that He was faithful to the promise He made to Abraham. Although the engagement gift had been given, Mary and Joseph had not yet been physically intimate.
Before a man ever touched her, Mary was found with child. Our natural inclination is to reject such a claim. Only by the assurance of the Holy Ghost can we believe that this is true. Yet, for the surety of our salvation, it must be true.
I read a paper written by a doctor many years ago that indicated that the components that make blood come from our fathers. This is not the same thing as blood type which is affected by both the father and the mother. That Jesus was conceived of the Holy Ghost is significant in that His blood was not tainted with the Adamic nature. That He was born of a virgin resonated with the Jews because of the prophecy from Isaiah.
The hand of the Lord was upon Mary in the birth of Jesus. God also blessed her in the fact that Joseph obviously loved her. Even though it appeared on the surface that Mary had been unfaithful to Joseph, he did not want her publicly humiliated or even possibly stoned (Deuteronomy 22:23-24). God’s hand was in the matter to preserve Mary’s espousal to Joseph, to save her life, and to keep His promise of one who would redeem His people.