Mary who was betrothed to Joseph suddenly found herself pregnant.This is in accordance to Isaiah 7:14
Tracing back to the Old Testament, we see that it was a prophecy of prophet Isaiah which was being made manifest. Now, anyone could have been used by God,but why did He specifically choose her? (story for another day). Upon the annunciation, Angel Gabriel delivered a message to Mary telling her she will be over shadowed by the Holy Spirit and conceive a child.Mary was shocked and confused but, could she refuse the purpose of God? No!
Mary never had intercourse with anyone,therefore,the birth of Christ was pure and sinless unlike the case of other humans. We can therefore agree with the fact that God came down to earth in the likeness of human form, God is pure and without sin, which is why He chose Mary to birth the saviour.
Despite being God, He chose to be born in the most humble way, little wonder Herod was jealous. In summary, Mary birthing Jesus Christ was already prophesied in the Old Testament, which was about 400 years before Christ was born, isn't it wonderful, yes it is. God said "even before you were born, I know you". This is an interesting story,always believe in God, keep yourself Holy and remember to communicate with Him daily. Remember the closer you are to Him, the better your life becomes.
PS:read my next post on Mary's parents,her childhood and dedication to God.
Thanks for reading, I love you but God loves you more

virgin simply means the child was born without sin, so who made sex a sinful act? simply put the writer of the Bible and other holy books. now it will take an advanced mind and reason to see were that is coming from. the writers men. what is men's view of sexual act not been performed by himself, now men most times don't see sex the way women do that is why it is very easy for women to forgive a cheating man than for man to forgive a cheating woman. the bottom line is men usually sees a woman he likes sex act with another man as quite disgusting hence the very origin of the reason sex act is a sin.
come to think of it if everyone inherited sin from their parent because they are descendants of Adam, then Jesus himself inherited sin from the mother because she is a descendant of Adam