Could you please point me to the specific passage in the Bible which states that abortion is the terrible wrong you claim it to be?
The short answer: "No." (Well, Yes, Exodus 20:13)
Neither can I point you to the specific passage in the Bible that states that God is Triune. Rather, what we know about the Triune nature and substance of God, and what we know about what God thinks about the murder of unborn children in the womb is learned by getting to know God.
We know, for instance that God is the giver of life in general, initially and continually (Genesis 1-2; Acts 17:25). We also know that it is God who "opens the womb" and creates a child within the womb of a woman. This we know not so much from a direct statement (although I think it is stated), as from the narative and example after example. For instance: Jacob, through the deceipt of his father-in-law, ended up with two wives. He loved Rachel and did not love Leah. God saw that Leah was not loved, and He gave her a child by Jacob (Genesis 29:31). Then, Rachel was tormented because she had no child and God "opened her womb" (Genesis 30:22). These are just a scraping of the surface of the explicitely stated involvement of God in the conceiving of children. We could also talk about the midwives in Egypt, Sarah, Hannah, Ruth, Bethsheba, Elizabeth, Mary. If we have eyes to see, then we can look at Mildred, my grandmother who was given five sons, and, finally a daughter, who was my mother, Viola. (The gifts handed down to Viola and James, and to me are for another post.) I know of a woman who could not have children. She went through rigorous, expensive, and heart wrenching fertility treatments to no avail. Finally, giving up, the Lord opened her womb, and she has a little girl following her around as she carries her second-born in her arms. I know another woman who was protecting herself from pregnancy by several methods, and still the Lord opened her womb, and gave her a child, who has been an unexpected blessing.
God explicitely tells us that He gives children, and that they are a blessing or reward in Psalm 127:3-5.
God gives us a glimpse of His involvement in our growth and development in Psalm 139:13-16.
All of the above contributes to the conclusion that when God tells us that He knew Joshua, Esau and Jacob, and John while still in the womb that He knows each child in the womb, because He is directly involved in their creation, growth, and development.
God forbids murder (Exodus 20:13) and then the Bible continues throughout to define murder as the taking of innocent life (http://www.gnpcb.org/esv/search/?q=murder); and exacting punishment for murder (death).
If you, like I, have a wicked heart, and are still saying, "Yes, but so far you haven't shown me that God says, 'Thou shalt not abort your unborn child,'" there are two more places to look. If you insist on not seeing it, please let me know. I know the One, the only One who can change your mind and your heart.
In Amos 1:13, God was expecially angry with the Ammonites who tore open the wombs of pregnant women and killed their babies. "But look at the vicious damage they did to the women, this was what angered God! Abortion is safe for women now." No, look again. "...that they might enlarge their borders." It was not the women who threatened the Ammonite wealth enlargement, but those children in the womb, who would use up those resources. This was a vicious killing of innocent blood for the purpose of preserving wealth for those who are strong. And don't kid yourself about women not being hurt by abortion.
In Exodus 21:22-25 God tells the people (because like us, they had to have "what-if" laws to keep them from justifying themselves) that if two men are fighting, and one hits a pregnant woman, if the baby is born early, but well, the one who hit her will pay a fine, whatever the husband thinks is right. If the baby dies or is hurt, the laws apply as if that person were a person (life for life, eye for eye, tooth for tooth, hand for hand, foot for foot, burn for burn, wound for wound, stripe for stripe.).
The language that GOd gave His people at the time, Hebrew, used the same word for a child whether that child had been born, or not. That's as refreshing as it is significant.