First of all, there is an important distinction to make. Christians do not believe this because they are Christians; they believe this because it is what God says. “For you created my inmost being; you knit me together in my mother’s womb” (Psalm 139:13). Over and over in Scripture, we see that life is sacred to God.
The battle over abortion rights is part of the age-old battle that dates all the way back to the fall of Satan. It represents the desire for God-like power and authority. This power hunger was Satan’s downfall just as it was the catalyst to the demise of Adam and Eve, thus the entire human race. Abortion is another way people play “God.” God says, “NO!”
“What about in the case of rape?” God says, “NO!” “What about to save the life of the mother?” God says, “NO!” God does not allow His people to choose when morality applies. There are no reasons for which God would ordain the taking of an innocent life. God agonizes over a young girl who is raped. He longs for her to turn to Him so that He can show her His mercy and love in the midst of her pain. But, never does He want her to end the innocent life of a baby. Murder is not only wrong, but the act would also only intensify the agony that the woman suffers already.
God never promises that this life will be easy. But, even in the midst of the hardships, He calls us to certain standards. They are non-negotiable.
For further study on this issue, see the questions, “I have had an abortion. Will God forgive me?” and “Is abortion really murder?”
See also: Exodus 20:13, 21:22; Job 10:8-12; Psalms 22:10, 51:5, 127:3; Jeremiah 1:4-5.