If your worry is that a mother whose life is in danger will not be able to get an abortion, then in keeping with the rest of our laws and morality, there should be a self defense exception which allows a mother to get an abortion if her own life is in danger.

But there is some dispute about when the unborn is "a being", so we err on the side of killing them? You can say that you are erring on the side of freedom, but when it comes to taking a life, personal freedom should be, and is, restrained in favor of another's right to life.

We heavily regulate the taking of life. In fact, you generally can only do it in defense of your own life or somebody else's. And even then your actions will be scrutinized to ensure that a killing was indeed in self defense.

This does not rely on any religious argument, but if you would like to take religion into account (assuming a judeo/christian background) then it is beyond simple. God has commanded us not to kill. If we are unsure about the status of babies in the womb then the only reasonable and safe position, morally speaking, is to err on the side of life. I believe that most christians would agree that shedding innocent blood is at or near the top of the worst sins you can commit. Yet we cavalierly allow the killing of the unborn in the mother's womb when at best we are not sure how God views it.

Christians have something else to go on besides just common sense and the pure feeling of wrongness that accompanies the idea of killing the unborn. The early church fathers have spoken out against abortion. What weight do they hold? If you are a trinitarian christian they must hold some weight.