The fetus is just a part of the pregnant woman's body, like her tonsils or appendix. The child may die, and the mother live, or the mother may die, and the child live, proving they are two separate individuals. The unborn child takes an active role in his own development, controlling the course of the pregnancy, and the time of birth. Being inside something is not the same as being part of something. Human beings should not be discriminated against because of their place of residence.
Every woman has the right to choose.
It would be unfair to restrict a woman's choice by prohibiting abortion. Any civilized society restricts the individual's freedom to choose whenever that choice would harm an innocent person. People who are prochoice about abortion are often not prochoice about other issues with less at stake. Everyone is prochoice when it comes to the choices prior to pregnancy and after birth. Nearly all violations of human rights have been defended on the grounds of the right to choose.