What is the biblical basis for the claim that abortion is immoral? The Catholic Church, as well as many other Christians, believes that abortion is inherently immoral, based on the belief that life begins at conception.

What is the biblical basis for this position?

I'm interested in the perspective of those who are Biblical literalists, whether Protestant, Catholic, or others.
One of the most important passages regarding this is found in the Mosaic Law which God gave to Israel to be used in governance:


  "When men strive together and hit a pregnant woman, so that her
  children come out, but there is no harm, the one who hit her shall
  surely be fined, as the woman’s husband shall impose on him, and he
  shall pay as the judges determine. But if there is harm, then you
  shall pay life for life, eye for eye, tooth for tooth, hand for hand,
  foot for foot, burn for burn, wound for wound, stripe for stripe. 
  Exodus 21:22-25 ESV


So, if the child (and this is what it is called) is born but is unharmed, then the man is guilty of assault, which did not carry the death penalty.  However, if the child IS harmed, then the man's punishment should be the same as that which was suffered by the child while still in the womb.

From a biblical perspective, then, the taking of the life of an unborn child was considered murder and would receive capital punishment, accordingly.

In addition to this, John the Baptist responded the presence of God Incarnate when Mary visited his mother Elizabeth while both of them were still in the womb:


  In those days Mary arose and went with haste into the hill country, to
  a town in Judah, and she entered the house of Zechariah and greeted
  Elizabeth. And when Elizabeth heard the greeting of Mary, the baby
  leaped in her womb. And Elizabeth was filled with the Holy Spirit,
  and she exclaimed with a loud cry, "Blessed are you among women, and
  blessed is the fruit of your womb! And why is this granted to me that
  the mother of my Lord should come to me? For behold, when the sound of
  your greeting came to my ears, the baby in my womb leaped for joy. And
  blessed is she who believed that there would be a fulfillment of what
  was spoken to her from the Lord."  Luke 1:39-45 ESV


Before this, the angel told Zechariah the his son John (the Baptist) would be filled with the Holy Spirit even while in the womb of Elizabeth.


  for he will be great before the Lord. And he must not drink wine or
  strong drink, and he will be filled with the Holy Spirit, even from
  his mother’s womb.  Luke 1:15 ESV


Psalm 139 also speaks of life in the womb:


  For you formed my inward parts; you knitted me together in my mother’s womb. Psalm 139:13 ESV


Not only does life exist in the womb, but God is active in the creation of that life.

Summary

So, God gave Israel instructions to punish anyone who killed or harmed an unborn child, and the Bible strongly supports the position that life begins at conception and is in the image of God at that point, with a body, soul, and spirit.