To be realistic... government can and does take away life, and permit the taking of life, all the time. In war, in death penalty cases, in laws that permit people to defend themselves and their property. The right to life is not absolute, obviously. There are lots of situations where value judgments about the value of one life over another are made.
When the constitution was written there were living breathing speaking people in this country that were not acknowledged to have any right to life or liberty. Obviously the framers did not feel it was absolute either. Slaves were not considered to be human beings or citizens covered under the constitution, so I don't think we can argue the framers were intending to cover a fertilized egg or immature growing fetus in the womb.
Feel free to argue we should put into law what was not made clear in the original constitution, but I don't think the constitution covers abortion as it is now. That's why we have all the debate, and the law as it is now.
Congress has never passed a law saying it is ok for a woman to have an abortion.