The Root of the Opposition is Deeply Religious.
Angels are believed to be assigned to children to watch over them in heaven according to some Christian tradition and religion.
When the Angel Gabriel was sent to the Virgin Mary he was giving her news of her pregnancy and also likely of his assignment.
The Angel Gabriel told the Virgin Mary-you are going to conceive and be with child. This was an announcement of something already known in heaven to happen in the future. Christians believe that God knows who children are going to be sent to earth through the DNA coding of a human before they are sent.
"I knew you before you were knit together in your mother's womb"- this is a bible verse from the Old or First Hebrew Testament.
So a pregnancy of a human is not some accident of biology however it is conceived. Children made in the image of God come from God and are sent by God through the instrumentality of human intercourse (and only in one case without it.)
Once Gabriel announced to the Virgin Mary she was going to conceive a child she had two choices. She chose to say Yes, bring it on- Let it be done to me as you have said.
She could have said "are you kidding! I am not married yet, look at this hovel of a one room apartment i live in-how do you expect me to raise a child in this- and where are we going to get the money, i'm still paying off student loans, it's my body my business, how dare you enslave me as a breeding machine to your power tripping male angel chauvinist mentality-i'm moving forward with my life, bugger off."
That might have started a different religion. And it appears it has- because that is the spiritual foundation of the Pro-Choice Religion.